# J/Psi Preprints

• QCD coherence effects in high energy reactions with nuclei
J. Raufeisen
In this work, coherence effects in deep inelastic scattering (DIS) and in the Drell-Yan (DY) process off nuclei are investigated, in particular nuclear shadowing. The target rest frame and the color dipole formulation are employed. Multiple scatterings are treated in Glauber-Gribov theory, which is modified to include the nuclear form factor to all orders. Based on the mean coherence length, which is defined in this work, it is estimated that gluon shadowing is negligible at x_{Bj}>0.01. Parameter free calculations are compared to NMC and E665 data for DIS and to E772 data for DY. In both cases, good agreement is found. It is however not possible to reproduce the effect observed by HERMES. For dileptons in proton-nucleus collisions at RHIC energies, considerable shadowing for the whole x_F range is predicted. The influence of the nucleus on the DY transverse momentum distribution is also studied. Furthermore, a new parametrization of the dipole cross section is presented.
SPIRES or http://arXiv.org/abs/hep-ph/0009358
• QCD Radiation off Heavy Particles
E. Norrbin and T. Sj\"ostrand
We study QCD radiation in decay processes involving heavy particles. As input, the first-order gluon emission rate is calculated in a number of reactions, and comparisons of the energy flow patterns show a non-negligible process dependence. To proceed further, the QCD parton shower language offers a convenient approach to include multi-gluon emission effects, and to describe exclusive event properties. An existing shower algorithm is extended to take into account the process-dependent mass, spin and parity effects, as given by the matrix element calculations. This allows an improved description of multiple gluon emission effects off b and t quarks, and also off nonstandard particles like squarks and gluinos. Phenomenological applications are presented for bottom production at LEP, Higgs particle decay to heavy flavours, top production and decay at linear colliders, and some simple supersymmetric processes.
SPIRES or http://arXiv.org/abs/hep-ph/0010012
• The charmed and bottom meson spectrum from lattice NRQCD
Randy Lewis and R. M. Woloshyn
The mass spectrum of S and P-wave mesons containing a single heavy quark has been computed using quenched lattice nonrelativistic QCD. Numerical results have been obtained at first, second and third order in the heavy quark expansion, so convergence can be discussed. The computed spectrum of charmed and bottom mesons is compared to existing model calculations and experimental data.
SPIRES or http://arXiv.org/abs/hep-ph/0010013
• Equation of State in Quantum Chromodynamics
V.I. Yukalov, E.P. Yukalova
The equation of state for quark-gluon plasma is obtained, being valid for arbitrary values of the coupling parameter and of temperature. This equation is constructed from perturbative expansions for free energy and for renormalization function. Summation of asymptotic perturbative series is accomplished by means of the self-similar approximation theory.
SPIRES or http://arXiv.org/abs/hep-ph/0010028
• Hadronic interactions of the J/psi
Kevin L. Haglin (SCSU) and Charles Gale (McGill)
We calculate the cross sections for reactions of the J/psi with light mesons. We also evaluate its finite temperature spectral function. We investigate separately the role of elastic and inelastic channels and we compare their respective importance. We describe J/psi absorption channels that have not been considered previously to our knowledge. The relevance of our study to heavy ion collisions is discussed.
SPIRES or http://arXiv.org/abs/nucl-th/0010017

SPIRES or www
• Searching Saturation in eA Processes
V. P. Goncalves (IFM - UFPel)
The high density effects should be manifest at small x and/or large nuclei. In this letter we consider the behavior of nuclear structure function $F_2^A$ slope in the kinematic region which could be explored in the future eA colliders as a search of these effects. We verify that the high density implies that the maximum value of the slope occurs at large values of the photon virtuality, i.e. in a perturbative regime, and is dependent of the number of nucleons A and energy. Our conclusion is that the measurement of this observable will allow to explicit the saturation.
SPIRES or http://arXiv.org/abs/hep-ph/0010060
• Multiplicity of different hadrons in e+e-, pp, and AA collisions
H. Drescher, J. Aichelin, and K. Werner
Employing the recently developed neXus model, we compare the yields of different hadrons in ultra-relativistic collisions: electron-positron annihilation at 91 GeV, proton-proton scattering at 17 GeV and nucleus-nucleus collisions at 17 GeV (SPS) and 200 GeV (RHIC). Plotting the yields as a function of the hadron masses, we find very surprising results: we observe that the spectra are practically identical for e+e- at 91 GeV and central nucleus-nucleus reactions at SPS and RHIC energies, whereas the spectrum for proton-proton scattering is somewhat steeper. All have the form one expects if the particles were emitted by a canonical system which is characterized by a temperature and chemical potentials. These identical forms have, however, different origins: in e+e- and pp the exponential shape it is due to the statistical behavior of string fragmentation, which has absolutely nothing to do with thermalization, in AA it is caused by phase space. The fact that e+e- and nuclear results agree is pure coincidence. Surprisingly the results for pp and e+e- differ, although here the production mechanism is identical. In pp collisions we see directly that the string energy is very limited and hence the high mass baryons are suppressed. We conclude that it is practically impossible to draw conclusions from hadronic yields about the reaction mechanism.
SPIRES or http://arXiv.org/abs/hep-ph/0010094
• When can long-range charge fluctuations serve as a QGP signal?
E.V. Shuryak and M.A. Stephanov
We critically discuss recent suggestion to use long-range modes of charge (electric or baryon) fluctuations as a signal for the presence of Quark-Gluon Plasma at the early stages of a heavy ion collision. We evaluate the rate of diffusion in rapidity for different secondaries, and argue that for conditions of the SPS experiments, it is strong enough to relax the magnitude of those fluctuations almost to its equilibrium values, given by hadronic resonance gas''. We further argue that experimental data from SPS agree with this conclusion. We evaluate the detector acceptance needed to measure such primordial'' long-range fluctuations at RHIC conditions. We conclude with an application of the charge fluctuation analysis to the search for the QCD critical point.
SPIRES or http://arXiv.org/abs/hep-ph/0010100
• Probing For New Physics In J/$\Psi$ Decays
X. Zhang (IHEP, Beijing)
Beijing Spectrometer (BES) at Beijing Electron Positron Collider (BEPC), IHEP has accumulated 2.5 $\times 10^7$ J/$\Psi$ and plans to increase the number to $10^8 \sim 10^9$ in the near future. In this paper I review and summarize the recent studies on the possibilities of probing for new physics at BES. This includes the theoretical works on and experimental attempt performed at BES in searching for flavor changing neutral current, CP violation and lepton flavor violation in the processes of J/$\Psi$ decays.
SPIRES or http://arXiv.org/abs/hep-ph/0010105
• QCD sum rule analysis of the charmonium system: The charm quark mass
Markus Eidemuller and Matthias Jamin
In this work, the charm quark mass is obtained from a QCD sum rule analysis of the charmonium system. In our investigation we include results from non-relativistic QCD at next-to-next-to-leading order. Using the pole mass scheme, we obtain a value of $M_c=1.70\pm 0.13$ GeV for the charm pole mass. The introduction of a potential-subtracted mass leads to an improved scale dependence. The running ${\rm \MSb}$-mass is then determined to be $m_{c}(m_{c}) = 1.23 \pm 0.09$ GeV.
SPIRES or http://arXiv.org/abs/hep-ph/0010133
• J/psi and psi(2S) Production and Polarization at the Tevatron
Michael Kr\"amer (University of Edinburgh)
The NRQCD factorization approach for quarkonium production at hadron colliders is reviewed. The prediction of J/psi and psi(2S) transverse polarization at large transverse momentum is confronted with recent experimental data, and potential shortcomings of the theoretical analysis are discussed.
SPIRES or http://arXiv.org/abs/hep-ph/0010137
• Statistical Coalescence Model with Exact Charm Conservation
M.I. Gorenstein, A.P. Kostyuk, H. Stoecker and W. Greiner
The statistical coalescence model for the production of open and hidden charm is considered within the canonical ensemble formulation. The data for the J/psi multiplicity in Pb+Pb collisions at 158 A GeV are used for the model prediction of the open charm yield which has not yet been measured in these reactions.
SPIRES or http://arXiv.org/abs/hep-ph/0010148
• Quarks in nuclear medium
K. Saito
Using the quark-meson coupling (QMC) model we study nuclear matter from the point of view of quark degrees of freedom. As the nucleon model we adopt the MIT bag model and the relativistic constituent quark model, where a square well and harmonic oscillator potentials are used to confine the quarks. We introduce the Lorentz-vector type confining potential as well as the Lorentz-scalar type one in order to examine how the vector confining potential contributes to the properties of the nucleon and nuclear matter. Next, we perform a re-definition of the scalar field in matter and transform the QMC model to a QHD-type model with a non-linear scalar potential. The result obtained from QMC is then compared with the potentials which are determined so as to fit various properties of finite nuclei and nuclear matter in relativistic mean-field models. The QMC model provides the parameters $\kappa \sim 20 - 40$ (fm$^{-1}$) and $\lambda \sim 80 - 400$ for the standard, non-linear scalar potential. We discuss a relationship between the QMC and QHD-type models in detail.
SPIRES or http://arXiv.org/abs/nucl-th/0010035

SPIRES or www
• Coherent particle production in collisions of relativistic nuclei
George L. Gogiberidze (JINR & IUCF), Edward K.G. Sarkisyan (CERN & Tel
Here we give the results of our study of features of dense groups, or spikes, of particles produced in Mg-Mg and C-Cu collisions at, respectively, 4.3 and 4.5 GeV/c/nucleon aimed to search for a coherent, Cerenkov-like, mechanism of hadroproduction. We investigate the distributions of spike centers and, for Mg-Mg interactions, the energy spectra of negatively charged particles in spikes. The spike-center distributions are obtained to exhibit the structure expected from coherent gluon-jet emission dynamics. This structure is similar in both cases considered, namely for all charged and negatively charged particles, and is also similar to that observed recently for all-charged-particle spikes in hadronic interactions. The energy distribution within spikes is found to have a significant peak over the inclusive background, while the inclusive spectrum shows exponential decrease with two characteristic values of average kinetic energy.The value of the peak energy and its width are in a good agreement with those expected for pions produced in a nuclear medium in the framework of the Cerenkov quantum approach. The peak energy obtained is consistent with the value of the cross-section maximum observed in coincidence nucleon-nucleus interaction experiments.
SPIRES or http://arXiv.org/abs/hep-ph/0010190
• QCD factorization with heavy quarks
German Rodrigo (Karlsruhe U.) and Marcello Ciafaloni (Florence U. &
We further analyze the definition and the calculation of the heavy quark impact factor at next-to-leading (NL) $\log s$ level, and we provide its analytical expression in a previously proposed k-factorization scheme. Our results indicate that k-factorization holds at NL level with a properly chosen energy scale, and with the same gluonic Green's function previously found in the massless probe case.
SPIRES or http://arXiv.org/abs/hep-ph/0010216
• Kinematic Effects in Radiative Quarkonia Decays
Stefan Wolf (TTP, U. of Karlsruhe)
Non-relativistic QCD (NRQCD) predicts colour octet contributions to be significant not only in many production processes of heavy quarkonia but also in their radiative decays. We investigate the photon energy distributions in these processes in the endpoint region. There the velocity expansion of NRQCD breaks down which requires a resummation of an infinite class of colour octet operators to so-called shape functions. We model these non-perturbative functions by the emission of a soft gluon cluster in the initial state. We found that the spectrum in the endpoint region is poorly understood if the values for the colour octet matrix elements are taken as large as indicated from NRQCD scaling rules. Therefore the endpoint region should not be taken into account for a fit of the strong coupling constant at the scale of the heavy quark mass.
SPIRES or http://arXiv.org/abs/hep-ph/0010217
• J/psi absorption by pi and rho mesons in meson exchange model with anomalous parity interactions
Yongseok Oh, Taesoo Song, Su Houng Lee
We reanalyze the dissociation process of the $J/\psi$ by $\pi$ and $\rho$ mesons into $D + \bar{D}$, $D^* + \bar{D}$, $D + \bar{D}^*$, and $D^* + \bar{D}^*$ within a meson exchange model. In addition to the dissociation mechanisms considered in the literature, we consider anomalous parity interactions, whose couplings are constrained by heavy quark spin symmetry and phenomenology. This opens new dissociation channels and adds new diagrams in the previously considered processes. Compared to the previous results, we find that these new additions have only a minor effect on the $\rho + J/\psi$ total inelastic cross section, but reduce the one for $\pi + J/\psi$ by about 50 % near the threshold.
SPIRES or http://arXiv.org/abs/nucl-th/0010064
• Soft Pomeron in QCD
Eugene Levin (Tel Aviv U. /DESY)
This is a talk, given at Diffraction'2000, Sept. 2 - 7, Centraro, Italy. This talk is a brief presentation of our view on the Pomeron, as a non-perturbative QCD phenomenon but from sufficiently short distances. Our approach is based on the scale anomaly of QCD and emphasizes the r{\^o}le of semi-classical QCD vacuum fields. We show that both the intercept and the slope of Pomeron trajectory appear to be determined by the energy density of non-perturbative QCD vacuum. The particular example of semi-classical QCD vacuum fields is discussed based on a new type of instanton-induced interactions (instanton ladder'') that leads to the rising with energy cross section $\sigma \sim s^{\Delta_P}$ of Regge type (the Pomeron).
SPIRES or http://arXiv.org/abs/hep-ph/0010271
• On the Character of Leading Asymmetry in the Hadroproduction of Charmed Mesons and Baryons
O.I.Piskounova (P.N.Lebedev Physical Institute, Moscow, Russia)
The character of asymmetry between the spectra of Lambda_c and antiLambda_c in the E781 experiment (FNAL) is discussed on the basis of the Quark Gluon String Model(QGSM). As it was shown in the description of the asymmetry between the spectra of leading and nonleading charmed mesons measured in Sigma^--A interactions at p_L= 340 GeV/c in the WA89 experiment in previous studies, the asymmetries between D^- and D^+ meson spectra and between D_s^- and D^+_s meson spectra can be fitted by QGSM curves with the same parameter of string fragmentation, a_1=10, as well as the asymmetry between the D-meson spectra in pion-nuclear collisions in the E791 experiment. The forms of Lambda_c/antiLambda_c asymmetry dependences measured in Sigma^-A and p-A collisions at p_L= 600 GeV/c in the E781 experiment are different . It is shown in the framework of QGSM that they depend on whether the diquarks of beam and target particles took part in charmed baryon formation or not. The QGSM results are compared with the calculations carried out by the other authors.
SPIRES or http://arXiv.org/abs/hep-ph/0010263
• Energy loss of fast quarks in nuclei
M.B. Johnson, B.Z. Kopeliovich, I.K. Potashnikova, P.L. McGaughey,
We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of $^2H$, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is $-dE/dz = 2.32 \pm 0.52\pm 0.5$ GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in nuclear environment.
SPIRES or http://arXiv.org/abs/hep-ex/0010051
• Excitation of Color Degrees of Freedom of Nuclear Matter and $J/\psi$ Suppression
J\"org H\"ufner, Boris Z. Kopeliovich and Alberto Polleri
In high energy nuclear collisions, the conventional Glauber model is commonly used to evaluate the contribution to $J/\psi$ suppression originating from the inelastic interaction with colorless bound nucleons. This requires an effective value for the $J/\psi$-nucleon absorption cross section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and find that these excited states provide a larger cross section for $J/\psi$ absorption. We conclude that the related corrections are important to explain the effective value extrapolated from experiment.
SPIRES or http://arXiv.org/abs/hep-ph/0010282
• The Role of Hadronization in Charm and Beauty Production
Yu.M.Shabelski (Petersburg Nuclear Physics Institute, Gatchina,
We discuss the relative role of fragmentation and recombination processes for heavy flavour hadron production in different kinematical regions in high energy hadron-hadron and photon-hadron collisions. We predict several qualitative features which should be observed if our picture of heavy flavour production is consistent.
SPIRES or http://arXiv.org/abs/hep-ph/0011032
• New Anomalous Exchange in Regge Phenomenology and Hard Diffraction
N.I. Kochelev,D.-P. Min, Y. Oh, V.Vento, A.V. Vinnikov
A new mechanism for hard diffraction based on the anomalous $f_1$ trajectory exchange, which we identify as the odd signature partner of the Pomeron, is suggested. We calculate the contribution of the $f_1$ exchange to elastic and dissociative electromagnetic production of vector mesons and show that it gives a dominant contribution to the differential cross sections at large momentum transfers.
SPIRES or http://arXiv.org/abs/hep-ph/0011042
• Massive c(\bar c)g-Production in Diffractive DIS
J. Bartels, H. Jung, A. Kyrieleis
We calculate the cross section for q(\bar q)g-production in diffractive DIS with finite fermion masses and zero momentum transfer. The calculation is done in the leading log(1/x_p) approximation and is valid for the region of high diffractive masses (small beta). We apply our cross section formula to diffractive charm production at HERA: in a Monte-Carlo-Simulation of diffractive D*+- meson production we include both massive q(\bar q)- and massive q(\bar q)g-production, and we compare with preliminary H1 results. After adjusting an infrared cutoff parameter of our model which affects the overall normalization of the cross section we find reasonable agreement with the data. In particular, the slope of the beta-distribution can be reproduced.
SPIRES or http://arXiv.org/abs/hep-ph/0010300
• Photoproduction of charm near threshold
S.J. Brodsky, E. Chudakov, P. Hoyer and J.M. Laget
Charm and bottom production near threshold is sensitive to the multi-quark, gluonic, and hidden-color correlations of hadronic and nuclear wavefunctions in QCD since all of the target's constituents must act coherently within the small interaction volume of the heavy quark production subprocess. Although such multi-parton subprocess cross sections are suppressed by powers of $1/m^2_Q$, they have less phase-space suppression and can dominate the contributions of the leading-twist single-gluon subprocesses in the threshold regime. The small rates for open and hidden charm photoproduction at threshold call for a dedicated facility.
SPIRES or http://arXiv.org/abs/hep-ph/0010343
• A simple solution to color confinement
Johan Hansson
We show that color confinement is a direct result of the nonabelian, i.e. nonlinear, nature of the color interaction in quantum chromodynamics. This makes it in general impossible to describe the color field as a collection of elementary quanta (gluons). A quark cannot be an elementary quanta of the quark field, as the color field of which it is the source is itself a source hence making isolated (noninteracting) quarks impossible. In geometrical language, the impossibility of quarks and gluons as physical particles arises due to the fact that the color Yang-Mills space does not have a constant trivial curvature.
SPIRES or http://arXiv.org/abs/hep-ph/0011060
• Debye Screening in the QCD plasma
O. Philipsen (CERN and MIT)
Various definitions for the QCD Debye mass and its evaluation are reviewed in a non-perturabtive framework for the study of screening of general static sources. While it is possible to perturbatively integrate over scales $\sim T$ and thus construct a 3d effective theory, the softer scales $\sim gT$ and $\sim g^2T$ are strongly coupled for temperatures $\lsim 10^7$ GeV and require lattice simulations. Within the effective theory, a lattice treatment of screening at finite quark densities $\mu \lsim 4/T$ is also possible.
SPIRES or http://arXiv.org/abs/hep-ph/0010327
• Topics in the Heavy Quark Expansion
Nikolai Uraltsev
Achievements in the heavy quark theory over the last decade are reviewed, with the main emphasis put on dynamical methods which quantify nonperturbative effects via application of the Operator Product Expansion. These include the total weak decay rates of heavy flavor hadrons and nonperturbative corrections to heavy quark sum rules. Two new exact superconvergent sum rules are derived; they differ from the known ones in that they are finite and normalization point independent in perturbation theory. A new hadronic parameter \bar\Sigma is introduced which is a spin-nonsinglet analogue of \bar\Lambda=M_B-m_b; it is expected to be about 0.25GeV. The first sum rule implies the bound \rho^2 > 3/4 for the slope of the Isgur-Wise function. The heavy quark potential is discussed and its connection to the infrared contributions in the heavy quark mass. Among applications extraction of |V_cb| from the total semileptonic and from the B->D^* zero recoil rates is addressed, as well as extracting |V_ub| from \Gamma_sl(b->u). Practical aspects of local quark-hadron duality are briefly discussed.
SPIRES or http://arXiv.org/abs/hep-ph/0010328
• Rho meson properties in nuclear matter from QCD sum rules
Andreas Nyffeler (CPT Marseille)
We study the properties of rho mesons in nuclear matter by means of QCD sum rules at finite density. For increased sensitivity, we subtract out the vacuum contributions. With the spectral function as estimated in the literature, these subtracted sum rules are found to be not well satisfied. We suppose that Landau singularities from higher resonance states in the nearby region in this channel are the cause for this failure.
SPIRES or http://arXiv.org/abs/hep-ph/0010329
• Charm quark mass from QCD sum rules for the charmonium system
M. Eidemuller and M. Jamin
In this work, the charm quark mass is obtained from a QCD sum rule analysis of the charmonium system. In our investigation we include results from nonrelativistic QCD at next-to-next-to-leading order. Using the pole mass scheme, we obtain a value of $M_c=1.70\pm 0.13$ GeV for the charm pole mass. The introduction of a potential-subtracted mass leads to an improved scale dependence. The running ${\rm \bar{MS}}$-mass is then determined to be $m_c(m_c) = 1.23 \pm 0.09$ GeV.
SPIRES or http://arXiv.org/abs/hep-ph/0010334
• Introduction to Diffractive Photoprocesses
G. Shaw (University of Manchester)
The objectives of my talk are to provide a very brief introduction to diffractive photoprocesses in general and the colour dipole model in particular; and to comment on possible gluon saturation effects at HERA and beyond.
SPIRES or http://arXiv.org/abs/hep-ph/0011007
• Screening length, dispersion relations and quark potential in thermo field dynamics
Wanyun Zhao and F.C. Khanna (Univ. of Alberta, Canada)
The screening length in a quark-gluon plasma, the dispersion relations of thermal gluon self-energy and the quark potential at high temperature are studied within thermo field dynamics framework. By calculation of the real and imaginary parts, of the gluon self-energy in one-loop order in thermo field dynamics, we obtain an expression for the screening length in a quark-gluon plasma and the dispersion relation between the real and imaginary parts. At high temperature, using photon exchange between electron-positron in a skeleton expansion and ladder approximation, the screened Coulomb potential is obtained, and using one-gluon and two-gluon exchange between a quark-antiquark, we get an expression for the screened quark potential up to $O(g amplitudes of generic process taking place in a many body system in equilibrium at temperature T. The relationship of the scattering and decay amplitudes as calculated in Thermo Field Dynamics to the conventional techniques is established. It is shown that in many cases the calculations are relatively easy in TFD. SPIRES or http://arXiv.org/abs/hep-ph/0011182 • Constraints on color dipole-nucleon cross section from diffractive heavy quarkonium production Katsuhiko Suzuki (Univ. of Tokyo), Kazunori Itakura (RBRC) We study the hard color dipole-nucleon cross section within perturbative QCD and discuss its relation to observables in diffractive leptoproduction of heavy quarkonium. The dipole cross section calculated with the unintegrated gluon density of the nucleon substantially differs from the well-known perturbative form$\sigma_{dip} \sim b^2$for$b > 0.3$fm, where$b$is the transverse separation of the dipole. We show the measured ratio of$\psi '$to$J / \psi$photoproduction cross sections constrains the dipole cross section at intermediate$b$, and in fact excludes the simple$\sigma_{dip} \sim b^2$behavior. We also calculate the$t$-slopes of the diffractive$J / \psi, \psi '$productions. We emphasize the difference of$t$-slopes,$B_{J/\psi} - B_{\psi '}$, is dominated by the dipole-nucleon dynamics. This difference is found to be about$0.3 {GeV}^{-2}$with our dipole cross section. SPIRES or http://arXiv.org/abs/hep-ph/0011186 • Some comments on the missing charm puzzle Alexander Lenz • A Toy Model of Colour Screening in the Proton Johann Dischler and Torbj\"orn Sj\"ostrand In hadronic collisions, the mini-jet cross section is formally divergent in the limit pT -> 0. We argue that this divergence is tamed by some effective colour correlation length scale of the hadron. A toy model of the hadronic structure is introduced, that allows an estimate of the screening effects, and especially their energy dependence. SPIRES or http://arXiv.org/abs/hep-ph/0011282 • Spin effects in diffractive hadron photoproduction S.V. Goloskokov We study spin asymmetries in diffractive$Q \bar Q$and vector meson production which are sensitive to the spin-dependent part of the two-gluon-nucleon coupling. It is found that the$A_{ll}$and$A_{lT}$asymmetry in diffractive reactions can be used to study polarized gluon distributions of the proton. SPIRES or http://arXiv.org/abs/hep-ph/0011341 • Color degrees of freedom in nuclear collisions and charmonium suppression J\"org H\"ufner, Boris Z. Kopeliovich and Alberto Polleri In high energy nuclear collisions, the Glauber model is commonly used to evaluate$J/\psi$suppression due to inelastic interaction with colorless bound nucleons. This requires an effective value for the$J/\psi$-nucleon absorption cross section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and conclude that the related corrections are important to explain the effective value extrapolated from experiment. SPIRES or http://arXiv.org/abs/hep-ph/0012010 • Open Charm Enhancement in Pb+Pb Collisions at SPS M.I. Gorenstein, A.P. Kostyuk, H. Stoecker and W. Greiner The statistical coalescence model for the production of open and hidden charm is considered within the canonical ensemble formulation. The data for the J/\psi multiplicity in Pb+Pb collisions at 158 A GeV are used for the model prediction of the open charm yield. We find a strong enhancement of the open charm production, by a factor of about 2--4, over the standard hard-collision model extrapolation from nucleon-nucleon to nucleus-nucleus collisions. A possible mechanism of the open charm enhancement in A+A collisions at the SPS energies is proposed. SPIRES or http://arXiv.org/abs/hep-ph/0012015 • Fluctuations of the transverse energy in Pb+Pb collisions and J/psi suppression J\"org H\"ufner, Boris Z. Kopeliovich and Alberto Polleri The observed$J/\psi$suppression in Pb+Pb collisions shows a break in the domain of large transverse energy. It has been proposed to extend the validity of existing models in this domain by introducing an ad hoc factor responsible for transverse energy fluctuations. We derive this result with some modifications. SPIRES or http://arXiv.org/abs/nucl-th/0012003 • Supersymmetric origin of a low$a_{J/\psi}$CP asymmetry A. Masiero, M. Piai (SISSA) and O. Vives (U. Valencia-IFIC) We show that general Minimal Supersymmetric extensions of the Standard Model (MSSM) allow for a CP asymmetry in B --> J/psi K(S) well bellow the SM expectations with dominant Supersymmetric contributions to epsilon_K and epsilon'/epsilon. Indeed, we provide an explicit example of an MSSM with non-universal soft breaking terms fully consistent with the low results of this asymmetry recently reported by Babar and Belle collaborations. SPIRES or http://arXiv.org/abs/hep-ph/0012096 • Heavy Flavour Physics: On Its More Than 50 Years Of History, Its Future And The Rio Manifesto I.I. Bigi After a reminder about how$\Delta S\neq 0$physics has been instrumental for the development of the Standard Model I sketch theoretical technologies for dealing with nonperturbative QCD in heavy flavour decays and state predictions for CP odd effects as they were made in 1998. I review the exciting developments in heavy flavour physics as presented at this conference. A central message is presented in the `Rio Manifesto' where I recapitulate the lessons we have learnt from charm physics, point out the special role future dedicated charm studies can play in revealing the presence of New Physics and give an introduction to the relevant phenomenology focussed on CP studies. SPIRES or http://arXiv.org/abs/hep-ph/0012161 • On the$\sigma_L/\sigma_T$Ratio in Polarized Vector Meson Photoproduction S.V.Goloskokov We study the spin-dependent cross-sections of vector meson photoproduction for longitudinally and transversely polarized photons within a QCD- model. The dependence of the$\sigma_T/\sigma_L$ratio on the photon virtuality and on the meson wave function is analysed. SPIRES or http://arXiv.org/abs/hep-ph/0012307 • Open and Hidden Charm Production in Au+Au Collisions at RHIC Energies M.I. Gorenstein, A.P. Kostyuk, L. McLerran, H. Stoecker and W. Greiner We consider various possibilities for the production of open charm and J/psi at RHIC energies in heavy ion collisions. We discuss several recently developed pictures for J/psi production and argue that a measurement at RHIC energies is crucial for disentangling these different descriptions. SPIRES or http://arXiv.org/abs/hep-ph/0012292 • J/Psi suppression in colliding nuclei: statistical model analysis Dariusz Prorok and Ludwik Turko We consider the$J/\Psi$suppression at a high energy heavy ion collision. An ideal gas of massive hadrons in thermal and chemical equilibrium is formed in the central region. The finite-size gas expands longitudinally in accordance with Bjorken law. The transverse expansion in a form of the rarefaction wave is taken into account. We show that$J/\Psi$suppression in such an environment, when combined with the disintegration in nuclear matter, gives correct evaluation of NA38 and NA50 data in a broad range of initial energy densities. SPIRES or http://arXiv.org/abs/hep-ph/0012382 • On the Energy Loss of High Energy Quarks in a Finite-Size Quark-Gluon Plasma B. G. Zakharov We study within the light-cone path integral approach the induced gluon emission from a fast quark passing through a finite-size QCD plasma. We show that the leading log approximation used in previous studies fails when the gluon formation length becomes of the order of the length of the medium traversed by the quark. Calculation of the energy loss beyond the leading log approximation gives the energy loss which grows logarithmically with quark energy contrary to the energy independent prediction of the leading log approximation. SPIRES or http://arXiv.org/abs/hep-ph/0012360 • Screening Corrections in Photo and DIS Production of$J/\Psi$E. Gotsman (Tel Aviv U.), E. Ferreira (UFRJ), E. Levin, U. Maor and E. Photo and DIS production of$J/\Psi$are investigated and compared with calculations based on pQCD in the LLA approximation without and with screening corrections. The calculation includes corrections induced by the real part of the production amplitude, the skewed (off diagonal) gluon structure function and the relativistic Fermi motion within the charmonium system. Our pQCD results are also compared with the predictions obtained from a Regge type two Pomeron model. Our results suggest some preference for our screened model, but the available data does not enable us to exclude any of the three models we have examined. The properties of these models, when extrapolated to both low and very high energies may provide a more effective discrimination between the different parameterizations. SPIRES or http://arXiv.org/abs/hep-ph/0101142 • Heavy Quark Production at High Energy R.D. Ball and R.K. Ellis We report on QCD radiative corrections to heavy quark production valid at high energy. The formulae presented will allow a matched calculation of the total cross section which is correct at$O(\as^3)$and includes resummation of all terms of order$\as^3 [\as \ln (s/m^2)]^n$. We also include asymptotic estimates of the effect of the high energy resummation. A complete description of the calculation of the heavy quark impact factor is included in an appendix. SPIRES or http://arXiv.org/abs/hep-ph/0101199 • A Unified Model of Exclusive$\rho^0$,$\phi$and$\jpsi$Electroproduction A Donnachie, J Gravelis and G Shaw (University of Manchester) A two-component model is developed for diffractive electroproduction of$\rho^0$,$\phi$and$\jpsi$, based on non-perturbative and perturbative two-gluon exchange. This provides a common kinematical structure for non-perturbative and perturbative effects, and allows the role of the vector-meson vertex functions to be explored independently of the production dynamics. A good global description of the vector-meson data is obtained. SPIRES or http://arXiv.org/abs/hep-ph/0101221 • Remarks on photon-hadron interactions E. Comay Theoretical aspects of VMD and related approaches to real photon-hadron interaction are discussed. The work relies on special relativity, properties of linearly polarized photons, angular momentum conservation and relevant experiments. It is explained why VMD and similar approaches should not be regarded as part of a theory but, at most, as phenomenological models. A further experiment pertaining to this issue is suggested. SPIRES or http://arXiv.org/abs/hep-ph/0101312 • Mott effect at the chiral phase transition and anomalous J/Psi suppression Gerhard R.G. Burau, David B. Blaschke, Yuri L. Kalinovsky We investigate the in-medium modification of the charmonium break-up processes due to the Mott effect for light (pi) and open-charm (D, D*) mesons at the chiral/deconfinement phase transition. A model calculation for the process J/Psi + pi -> D + \bar D* + h.c. is presented which demonstrates that the Mott effect for the D-mesons leads to a threshold effect in the thermal averaged break-up cross section. This effect is suggested as an explanation of the phenomenon of anomalous J/Psi suppression in the CERN NA50 experiment. SPIRES or http://arXiv.org/abs/nucl-th/0012030 SPIRES or www • J/\psi production through resolved photon processes at e+ e- colliders R.M. Godbole (IISc., Bangalore), D. Indumathi (IMSc., Chennai), M. We consider J/psi photoproduction in e+ e- as well as linear photon colliders. We find that the process is dominated by the resolved photon channel. Both the once-resolved and twice-resolved cross-sections are sensitive to (different combinations of) the colour octet matrix elements. Hence, this may be a good testing ground for colour octet contributions in NRQCD. On the other hand, the once-resolved J/psi production cross-section, particularly in a linear photon collider, is sensitive to the gluon content of the photon. Hence these cross-sections can be used to determine the parton distribution functions, especially the gluon distribution, in a photon, if the colour octet matrix elements are known. SPIRES or http://arXiv.org/abs/hep-ph/0101333 • Searches for Rare and Forbidden Decays of Charm: Recent Results from FNAL A. J. Schwartz We review results on rare and forbidden decays of D^0, D^+, and D^+_s mesons from experiments at FNAL. The decay modes studied have two leptons in the final state and, if observed, would constitute evidence for flavor-changing neutral-current, lepton-flavor-violating, or lepton-number-violating processes. To date, no evidence for these decays has been observed and upper limits are obtained for their branching fractions. These limits can constrain various extensions to the Standard Model. We present new upper limits from FNAL E791 on the branching fractions for more than two dozen three- and four-body decay modes. SPIRES or http://arXiv.org/abs/hep-ex/0101050 • Transverse energy distributions and$J/\psi$production in Pb+Pb collisions A. K. Chaudhuri We have analysed the latest NA50 data on transverse energy distributions and$J/\psi$suppression in Pb+Pb collisions. The transverse energy distribution was analysed in the geometric model, where AA collisions are written in terms of NN collisions, taking into account the fluctuations in the number of NN collisions at fixed impact parameter. Analysis suggests that in Pb+Pb collisions, nucleons are more transparent than in other AA collisions, producing less$E_T$in individual NN collisions. The transverse energy dependence of the$J/\psi$was obtained assuming that charmonium suppression is 100% effective above a threshold density. Good fit to data is obtained if the fluctuations in number of NN collisions at fixed impact parameter is taken into account. SPIRES or http://arXiv.org/abs/hep-ph/0102038 • Heavy-quarkonium hadron cross section in QCD at leading twist F. Arleo, P.-B. Gossiaux, T. Gousset, and J. Aichelin We compute the total cross section of a heavy quarkonium on a hadron target in leading twist QCD, including target mass corrections. Our method relies on the analytical continuation of the operator product expansion of the scattering amplitude, obtained long ago by Bhanot and Peskin. The cross section has a simple partonic form, which allows us to investigate the phenomenology of J/psi and Upsilon dissociation by both pions and protons. SPIRES or http://arXiv.org/abs/hep-ph/0102095 • The p_T Spectrum in Heavy-Flavour Photoproduction M. Cacciari, S. Frixione and P. Nason We consider the transverse-momentum distribution of heavy flavours in photon-hadron collisions. We present a formalism in which large transverse-momentum logarithms are resummed to the next-to-leading level, and mass effects are included exactly up to order alpha_em alpha_s^2, so as to retain predictivity at both small and large transverse momenta. Phenomenological applications relevant to charm photoproduction at HERA are given. SPIRES or http://arXiv.org/abs/hep-ph/0102134 • Gluon depletion and J/psi suppression in pA collisions R.C.Hwa The gluon distribution of a nucleon propagating through a nucleus can change depending on how far the penetration depth is. It is a nonperturbative process that we describe by an evolution equation. The kernel of the integral equation is to be determined by a phenomenological study of J/psi suppression in pA collision. The data of E866 on alpha(x_F) shows significant dependence on x_F at large x_F. It presents a feature that has not been explained by any hadronic absorption model. We show that gluon depletion is a simple mechanism that can account for it. The result has far-reaching implications on the role of partons in nuclear collisions. SPIRES or http://arXiv.org/abs/hep-ph/0102154 • Diffractive eta_c photo-and electroproduction with the perturbative QCD Odderon J. Bartels, M. A. Braun, D. Colferai, G. P. Vacca Using a set of new odderon states, we calculate their contribution to the diffractive eta_c photo- and electroproduction process. Compared to previous simple 3-gluon exchange calculations we find an enhancement of about one order of magnitude in the cross section. The t-dependence of the cross section exhibits a dip structure in the small t region. SPIRES or http://arXiv.org/abs/hep-ph/0102221 • Possible Color Octet Quark-Anti-Quark Condensate in the Instanton Model Thomas Schaefer Inspired by a recent proposal for a Higgs description of QCD we study the possible formation of a color-octet/flavor-octet quark-anti-quark condensate in the instanton liquid model. For this purpose we calculate two-point correlation functions of color-singlet and octet quark-anti-quark operators. We find long range order in the standard$<\bar{\psi}\psi>$channel, but not in the color-octet channel. We emphasize that similar calculations in lattice QCD can check whether or not a color-flavor locked Higgs phase is realized in QCD at zero temperature and baryon density. SPIRES or http://arXiv.org/abs/hep-lat/0102007 SPIRES or www • Radiative Corrections to the Single Spin Asymmetry in Heavy Quark Photoproduction N.Ya.Ivanov (YerPI) We analyze in the framework of pQCD the properties of the single spin asymmetry in heavy flavor production by linearly polarized photons. At leading order, the parallel- perpendicular asymmetry in azimuthal distributions of both charm and bottom quark is predicted to be about 20% in a wide region of initial energy. Using the soft gluon resummation formalism, we have calculated the next-to-leading order corrections to the asymmetry to next-to-leading logarithmic accuracy. It is shown that radiative corrections practically do not affect the Born predictions for the azimuthal asymmetry at energies of the fixed target experiments. Both leading and next-to-leading order predictions for the asymmetry are insensitive to within few percent to theoretical uncertainties in the QCD input parameters:$m_{Q}$,$\mu_{R}$,$\mu_{F}$,$\Lambda_{QCD}$and in the gluon distribution function. Our analysis shows that nonperturbative corrections to a$B$-meson azimuthal asymmetry due to the gluon transverse motion in the target are negligible. We conclude that measurements of the single spin asymmetry would provide a good test of pQCD applicability to heavy flavor production at fixed target energies. SPIRES or http://arXiv.org/abs/hep-ph/0102328 • On a possible manifestation of f_1 trajectory in J/psi photoproduction Dayeeta Roy (1), Toshiyuki Morii (2)and Alexander I. Titov (3) ((1) We analyze a possible manifestation of f_1-trajectory in elastic J/psi photoproduction at high energy and large momentum transfer. Inspite of the small contribution of f_1-trajectory in total cross sections, it becomes significant in various spin observables. In particular, we show that the crucial test for f_1-exchange can be made by measuring the single beam- and double parity- and beam-target asymmetries at large momentum transfers, where a strong deviation from the exchange of conventional Pomerons is expected. This effect is caused by the interference of natural (Pomeron) and unnatural (f_1) parity exchange parts of amplitude in the region where their contributions become comparable to each other and might be interesting to observe in forthcoming experiments, if feasible. . SPIRES or http://arXiv.org/abs/hep-ph/0103004 • Heavy Flavor Enhancement as a Signal of Color Deconfinement A.P. Kostyuk, M.I. Gorenstein and W. Greiner We argue that the color deconfinement in heavy ion collisions may lead to enhanced production of hadrons with open heavy flavor (charm or bottom). We estimate the upper bound of this enhancement. SPIRES or http://arXiv.org/abs/hep-ph/0103057 • Open charm enhancement by secondary interactions in relativistic nucleus-nucleus collisions? W. Cassing (Univ. of Giessen), L.A. Kondratyuk (ITEP Moscow), G.I. We calculate open charm production in$Pb+Pb$reactions at SPS energies within the HSD transport approach - which is based on string, quark, diquark ($q, \bar{q}, qq, \bar{q}\bar{q}$) and hadronic degrees of freedom - including the production of open charm pairs from secondary 'meson'-'baryon' (or quark-diquark and antiquark-diquark) collisions. It is argued that at collision energies close to the$c\bar{c}$pair threshold the dominant production mechanism is related to the two body (or quasi two body) reactions$\pi N \to \bar{D} (\bar{D^*}) \Lambda_c, (\Sigma_c)$. Estimates within the framework of the Quark-Gluon String model suggest cross sections of a few$\mu b$for$\pi N \to \bar{D} \Lambda_c$in the region of 1 GeV above threshold. The dynamical transport calculations for$Pb + Pb$at 160 A$\cdot$GeV indicate that the open charm enhancement reported by the NA50 Collaboration might be due to such secondary reaction mechanisms. SPIRES or http://arXiv.org/abs/hep-ph/0103073 • Thermal versus Direct$J/\Psi$Production in Ultrarelativistic Heavy-Ion Collisions L. Grandchamp and R. Rapp The production of$J/\Psi$mesons in central collisions of heavy nuclei is investigated as a function of collision energy. Two contributions are considered simultaneously: early (hard) production coupled with subsequent suppression in a Quark-Gluon Plasma, as well as thermal recombination of primordially produced$c$and$\bar c$quarks at the hadronization transition. Whereas the former still constitutes the major fraction of the observed$J/\Psi$abundance at SpS energies, the latter dominates the yield at RHIC. The resulting excitation function for the number of$J/\Psi$'s over open charm pairs exhibits nontrivial structure around$\sqrt{s} \simeq 30$AGeV, evolving into a significant rise towards maximal RHIC energy. We study this feature within different (thermal) scenarios for$J/\Psi$suppression, including parton-induced quasifree destruction as a novel mechanism. SPIRES or http://arXiv.org/abs/hep-ph/0103124 • On the size of hadrons Hans-Christian Pauli (1) and Asmita Mukherjee (2) ((1) MPI Kernphysik, The form factor and the mean-square radius of the pion are calculated analytically from a parametrized form of a$q\bar q$wave function. The numerical wave function was obtained previously by solving numerically an eigenvalue equation for the pion in a particular model. The analytical formulas are of more general interest than just be valid for the pion and can be generalized to the case with unequal quark masses. Two different parametrizations are investigated. Because of the highly relativistic problem, noticable deviations from a non-relativistic formula are obtained. SPIRES or http://arXiv.org/abs/hep-ph/0103150 • Gauge Invariance, Color-Octet Vector Resonances and Double Technieta Production at the Tevatron Alfonso R. Zerwekh and Rogerio Rosenfeld We show that the usual vector meson dominance method does not apply directly to the mixing of a color-octet vector boson (color-octet technirho) with the gluon because of gauge invariance. We propose a gauge invariant method where one works in a physical basis with mass eigenstate fields. As a result, we show that the physical technirho does not couple to two gluons, contrary to the general belief. Consequences for the production of a pair of color-octet, isosinglet technipions (technietas) at Fermilab is analysed by means of a simulation of the signal and background, including kinematical cuts. We find that the signal is too small to be observed. SPIRES or http://arXiv.org/abs/hep-ph/0103159 • Kaon and Charm Physics: Theory Gerhard Buchalla (CERN) We introduce and discuss basic topics in the theory of kaons and charmed particles. In the first part, theoretical methods in weak decays such as operator product expansion, renormalization group and the construction of effective Hamiltonians are presented, along with an elementary account of chiral perturbation theory. The second part describes the phenomenology of the neutral kaon system, CP violation,$\varepsilon$and$\varepsilon'/\varepsilon$, rare kaon decays ($K\to\pi\nu\bar\nu$,$K_L\to\pi^0 e^+e^-$,$K_L\to\mu^+\mu^-$), and some examples of flavour physics in the charm sector. SPIRES or http://arXiv.org/abs/hep-ph/0103166 • Generalized dipole polarizabilities and the spatial structure of hadrons A.I. L'vov (1), S. Scherer (2), B. Pasquini (3), C. Unkmeir (2), D. We present a phenomenological discussion of spin-independent, generalized dipole polarizabilities of hadrons entering the virtual Compton scattering process gamma* h -> gamma h. We introduce a new method of obtaining a tensor basis with appropriate Lorentz-invariant amplitudes which are free from kinematical singularities and constraints. We then motivate a gauge-invariant separation into a generalized Born term containing ground-state properties only, and a residual contribution describing the model-dependent internal structure. The generalized dipole polarizabilities are defined in terms of Lorentz-invariant residual amplitudes. Particular emphasis is laid on a physical interpretation of these quantities as characterizing the spatial distributions of the induced electric polarization and magnetization of hadrons. It is argued that three dipole polarizabilities, namely the longitudinal electric alpha_L(q^2), the transverse electric alpha_T(q^2), and the magnetic beta(q^2) ones are required in order to fully reconstruct local polarizations induced by soft external fields in a hadron. One of these polarizabilities, alpha_T(q^2), describes an effect of higher order in the soft final-photon momentum q'. We argue that the associated spatial distributions obtained via the Fourier transforms in the Breit frame are meaningful even for such a light particle as the pion. The spatial distributions are determined at large distances r ~ 1/m_pi for pions, kaons, and octet baryons by use of ChPT. SPIRES or http://arXiv.org/abs/hep-ph/0103172 • Heavy quarkonium production in double Pomeron exchange processes in perturbative QCD Feng Yuan (Heidelberg U.) We calculate the heavy quarkonium production in double pomeron exchange processes in perturbative QCD by using two-gluon exchange model. For the$P$-wave$\chi_J$productions, we find$\chi_1$and$\chi_2$production amplitudes which vanish in the forward scattering limit. We also calculate direct$J/\psi(\Upsilon)+\gamma$production in the same approach, and these direct contributions are much smaller than the feeddown contributions from the$P$-wave states. SPIRES or http://arXiv.org/abs/hep-ph/0103213 • Chiral Symmetry in Charmonium - Pion Cross Section F.S. Navarra, M. Nielsen and M.R. Robilotta We perform a non-perturbative calculation of the$J/\Psi-\pi$cross section using a$SU(2)\times SU(2)$effective Lagrangian. Our results differ from those of previous calculations, specially in the description of vertices involving pions. SPIRES or http://arXiv.org/abs/nucl-th/0103051 • Exclusive decay of$J/\Psi$into a lepton pair combined with light hadrons J.P. Ma We study the exclusive decay of$J/\Psi$into a lepton pair combined with light hadrons in the kinematic region, specified by that the total energy of the light hadrons is much smaller than$m_c$, the mass of the$c$-quark. In this region, the nonperturbaive effect related to$J/\Psi$and that related to the light hadrons can be separated, the former is represented by a NRQCD matrix element, while the later is represented by a matrix element of a correlator of electric chromofields. The results are obtained in a axial gauge by assumming that contributions from two-gluon emmssion are dominant. But we can show that these results can be obtained without the assumption in arbitrary gauges. A discussion of the results are presented. SPIRES or http://arXiv.org/abs/hep-ph/0103236 • Measurement of hybrid content of heavy quarkonia using lattice NRQCD Tommy Burch, Kostas Orginos, and Doug Toussaint Using lowest-order lattice NRQCD to create heavy meson propagators and applying the spin-flip interaction,$c_B^{} \frac{-g}{2m_q}\vec\sigma\cdot\vec{B}$, at varying intermediate time slices, we compute the off-diagonal matrix element of the Hamiltonian for the quarkonium-hybrid two-state system. Thus far, we have results for one set of quenched lattices with an interpolation in quark mass to match the$J^{PC}=1^{--}$bottomonium spectrum. After diagonalization of the two-state Hamiltonian, we find the ground state of bottomonium to show a$0.0035(1)c_B^2$(with$c_B^2 \sim 1.5-3.1$) probability admixture of hybrid,$|Q\bar{Q}g>$. SPIRES or http://arXiv.org/abs/hep-lat/0103025 • Heavy quark photoproduction at THERA P. Jankowski, M. Krawczyk (University of Warsaw), M. Wing (McGill Measurements of heavy quark production at a possible future$ep$facility, THERA, would provide valuable information on the structure of the photon. QCD cross-section predictions are made at LO for both charm and beauty production and their sensitivity to current parametrisations of the photon parton densities is investigated. SPIRES or http://arXiv.org/abs/hep-ph/0103330 • Charm Physics and the Poor Sleeper's Impatience I.I. Bigi After a short review of the theoretical tools available to describe heavy flavour physics I sketch the present profile of the weak dynamics of charm hadrons with respect to lifetimes, oscillations and CP violation. I argue that comprehensive studies of charm decays provide novel portals to New Physics and suggest some benchmark figures for desirable sensitivities. SPIRES or http://arXiv.org/abs/hep-ph/0104008 • J/Psi Production at RHIC in a QGP Robert L. Thews and Johann Rafelski In central collisions at RHIC, the initial production of heavy quarks will for the first time yield multiple pairs of c-cbar in each central event. If a region of deconfined quarks and gluons is subsequently formed, a new mechanism for the formation of heavy quarkonium bound states will be activated. This will result from the mobility of heavy quarks in the deconfined region, such that bound states can be formed from a quark and an antiquark which were originally produced in separate incoherent interactions. Our model estimates of this effect predict a dramatic increase in the number of observed J/Psi at RHIC, over that predicted from extrapolation of color-screening or gluon dissociation mechanisms from the lower CERN-SPS energies. The centrality and energy dependence of this effect should be readily observable by the Star and Phenix detectors. Thus the J/Psi abundance at RHIC will continue to provide a signature of QGP formation. However, it is in this environment a more useful probe, since contrary to prior expectations this large predicted J/Psi abundance should be relatively easy to measure. SPIRES or http://arXiv.org/abs/hep-ph/0104025 • Charmonium Production off Nuclei: from SPS to RHIC B.Z. Kopeliovich Physics of charmonium suppression in nuclear collisions drastically changes between the energies of SPS and RHIC. Mechanisms suppressing charmonia at SPS are reviewed, neither of which is important at RHIC. On the other hand, coherence, or shadowing of c-quarks and gluons barely seen at SPS, become a dominant effect at RHIC providing a much stronger suppression. A onset of coherence at Fermilab energies explains the observed cross section ratio steeply falling at large Feynman x_F. In nuclear collisions variation of charmonium suppression with x_F suggests a sensitive probe for QGP. SPIRES or http://arXiv.org/abs/hep-ph/0104032 • J/psi plus dijet associated production in two-photon collisions M. Klasen, B.A. Kniehl, L. Mihaila, M. Steinhauser (Hamburg We study the production of a J/psi meson in association with one or two jets in gamma gamma collisions concentrating on the direct-photon contribution, which is expected to be dominant for large J/psi-meson transverse momentum and/or large dijet invariant mass. We work at leading order in the factorization formalism of nonrelativistic QCD and include all relevant colour-octet processes. We present distributions in J/psi-meson transverse momentum and rapidity appropriate for CERN LEP2, a future e^+e^- linear collider, and a possible gamma gamma collider mode of the latter. In the case of the e^+e^- linear collider, we assume the beamstrahlung spectrum appropriate for DESY TESLA. SPIRES or http://arXiv.org/abs/hep-ph/0104044 • J/psi Suppression and Enhancement in Au+Au Collisions at the BNL RHIC M.I. Gorenstein, A.P. Kostyuk, H. Stoecker and W. Greiner We consider the production of the J/psi mesons in heavy ion collisions at RHIC energies in the statistical coalescence model with an exact (canonical ensemble) charm conservation. The c\bar{c} quark pairs are assumed to be created in the primary hard parton collisions, but the formation of the open and hidden charm particles takes place at the hadronization stage and follows the prescription of statistical mechanics. The dependence of the J/psi production on both the number of nucleon participants and the collision energy is studied. The model predicts the J/psi suppression for low energies, whereas at the highest RHIC energy the model reveals the J/psi enhancement. SPIRES or http://arXiv.org/abs/hep-ph/0104071 • Diffractive beauty photoproduction as a short distance probe of QCD pomeron V. R. Zoller (ITEP, Moscow) High-energy open beauty photoproduction probes the vacuum exchange at distances$\sim 1/m_b$and detects significant corrections to the BFKL asymptotics coming from the subleading vacuum poles. We show that the interplay of leading and subleading vacuum exchanges gives rise to the cross section$\sigma^{b\bar b}(W)$growing much faster than it is prescribed by the exchange of the leading pomeron trajectory with intercept$\alpha_{\Pom}(0)-1=\Delta_{\Pom}=0.4$. Our calculations within the color dipole BFKL model are in agreement with the recent determination of$\sigma^{b\bar b}(W)$by the H1 collaboration. The comparative analysis of diffractive photoproduction of beauty, charm and light quarks exhibits the hierarchy of pre-asymptotic pomeron intercepts which follows the hierarchy of corresponding hardness scales. We comment on the phenomenon of decoupling of soft and subleading BFKL singularities at the scale of elastic$\Upsilon(1S)$-photoproduction which results in precocious color dipole BFKL asymptotics of the process$\gamma p \to \Upsilon p$. SPIRES or http://arXiv.org/abs/hep-ph/0104093 • Interplay of soft and hard processes and hadron$p_T$spectra in$pA$and$AA$collisions Enke Wang and Xin-Nian Wang Motivated by a schematic model of multiple parton scattering within the Glauber formalism, the transverse momentum spectra in$pA$and$AA$collisions are analyzed in terms of a nuclear modification factor with respect to$pp$collisions. The existing data at the CERN Super Proton Synchrotron (SPS) energies are shown to be consistent with the picture of Glauber multiple scattering in which the interplay between soft and hard processes and the effect of absorptive processes lead to nontrivial nuclear modification of the particle spectra. Relative to the additive model of incoherent hard scattering, the spectra are enhanced at large$p_T$(hard) by multiple scattering while suppressed at low$p_T$(soft) by absorptive correction with the transition occurring at around a scale$p_0\sim 1-2$GeV/$c$that separates soft and hard processes. Around the same scale, the$p_T$spectra in$pp$collisions also change from an exponential form at low$p_T$to a power-law behavior at high$p_T$. At very large$p_T\gg p_0$, the nuclear enhancement is shown to decrease like$1/p_T^2$. Implications of these nuclear effects on the study of jet quenching, parton thermalization and collective radial flow in high-energy$AA$collisions are discussed. SPIRES or http://arXiv.org/abs/nucl-th/0104031 SPIRES or www • The color dipole approach to the Drell-Yan process in pA collisions B.Z. Kopeliovich, J. Raufeisen, A.V. Tarasov In the target rest frame and at high energies, Drell-Yan (DY) dilepton production looks like bremsstrahlung of massive photons, rather than parton annihilation. The projectile quark is decomposed into a series of Fock states. Configurations with fixed transverse separations are interaction eigenstates for pp scattering. The DY cross section can then be expressed in terms of the same color dipole cross section as DIS. This approach is especially suitable to describe nuclear effects, since it allows to apply Glauber multiple scattering theory. We go beyond the Glauber eikonal approximation by taking into account transitions between interaction eigenstates. We calculate nuclear shadowing at large Feynman-x_F for DY in proton-nucleus collisions, compare to existing data from E772 and make predictions for RHIC. Nuclear effects on the transverse momentum distribution are also investigated. SPIRES or http://arXiv.org/abs/hep-ph/0104155 • The photoproduction of vector mesons J.-M. Laget At high energy, the photoproduction or electroproduction of Vector Mesons allow to prepare a beam of quark-antiquark pairs of a given flavor. At high momentum transfer, the study of the scattering of these pairs on a nucleon opens up an original window on the quark-gluon structure of hadronic matter, which may eventually shed light on its gluonic content, on correlations between quarks and on the van der Walls part of the interaction between hadrons. SPIRES or http://arXiv.org/abs/hep-ph/0107208 • Color Transparency versus Quantum Coherence in Electroproduction of Vector Mesons off Nuclei B.Z. Kopeliovich, J. Nemchik, A.Schaefer, A.V. Tarasov So far no theoretical tool for the comprehensive description of exclusive electroproduction of vector mesons off nuclei at medium energies has been developed. We suggest a light-cone QCD formalism which is valid at any energy and incorporates formation effects (color transparency), the coherence length and the gluon shadowing. At medium energies color transparency (CT) and the onset of coherence length (CL) effects are not easily separated. Indeed, although nuclear transparency measured by the HERMES experiment rises with Q^2, it agrees with predictions of the vector dominance model (VDM) without any CT effects. Our new results and observations are: (i) the good agreement with the VDM found earlier is accidental and related to the specific correlation between Q^2 and CL for HERMES kinematics; (ii) CT effects are much larger than have been estimated earlier within the two channel approximation. They are even stronger at low than at high energies and can be easily identified by HERMES or at JLab; (iii) gluon shadowing which is important at high energies is calculated and included; (iv) our parameter-free calculations explain well available data for variation of nuclear transparency with virtuality and energy of the photon; (v) predictions for electroproduction of \rho and \phi are provided for future measurements at HERMES and JLab. SPIRES or http://arXiv.org/abs/hep-ph/0107227 •$J/\Psi$suppression in an expanding hadron gas Dariusz Prorok (Wroclaw Univ. ITP) A model for$J/\Psi$suppression at a high energy heavy ion collision is presented. The main (and the only) reason for the suppression is$J/\Psi$inelastic scattering within hadron matter. The hadron matter is in the form of a multi-component non-interacting gas. Also the evolution of the gas, both longitudinal and transverse, is taken into account. It is shown that under such circumstances and with$J/\Psi$disintegration in nuclear matter added,$J/\Psi$suppression evaluated agrees well with NA38 and NA50 data. SPIRES or http://arXiv.org/abs/hep-ph/0107260 •$J/\Psi$suppression at SPS, RHIC and LHC energies and the percolation of strings N. Armesto, E. G. Ferreiro, F. del Moral and C. Pajares We study the enhancement of$c \bar c$pair production that takes place in central heavy ion collisions due to the formation of clusters of strings. These clusters produce heavy flavors more efficiently due to their higher color. We discuss the competition between this mechanism and the well-known screening of color charge, which, above a critical string density, reduces strongly the probability of binding these$c \bar c$pairs to form$J/\Psi$particles. The dependence of$J/\Psi$suppression on the centrality shows a peak at both RHIC and LHC energies corresponding to the percolation critical density. SPIRES or http://arXiv.org/abs/hep-ph/0107319 • Quarkonium spectroscopy and perturbative QCD: massive quark-loop effects N. Brambilla, Y. Sumino and A. Vairo We study the spectra of the bottomonium and B_c states within perturbative QCD up to order alpha_s^4. The O(Lambda_QCD) renormalon cancellation between the static potential and the pole mass is performed in the epsilon-expansion scheme. We extend our previous analysis by including the effects of non-zero charm-quark mass in loops up to the next-to-leading non-vanishing order epsilon^3. An extensive quantitative analysis is provided. Qualitatively the effect of the charm mass is to widen the level spacings and the effect becomes larger among higher levels. The size of non-perturbative and higher order contributions is discussed by comparing the obtained predictions with the experimental data. An agreement of the perturbative predictions and the experimental data depends crucially on the precise value (inside the present error) of alpha_s(M_Z). For the b-quark MSbar mass we obtain$m_b^{\overline{MS}}(m_b^{\overline{MS}}) = 4190 \pm 20 \pm 25 \pm 4 ~ {MeV}$. SPIRES or http://arXiv.org/abs/hep-ph/0108084 • QCD Sum Rules for Heavy Flavour Physics Alexander Khodjamirian Uses of QCD sum rules for heavy flavoured hadrons are discussed. "Standard" applications such as the determination of the$b$,$c$quark masses, the calculation of$f_B$,$f_D$and of the heavy-to-light form factors are overviewed. Furthermore, a new approach to calculate the$B\to \pi\pi$hadronic matrix elements from QCD light-cone sum rules is described. SPIRES or http://arXiv.org/abs/hep-ph/0108205 • Explicit Proof that Electroproduction of Transversely Polarized Vector Mesons Vanishes in Perturbative QCD Pervez Hoodbhoy (University of Maryland and Quaid-e-Azam University) By means of an explicit one-loop calculation, it is shown that the leading twist contribution to the exclusive electroproduction of transversely polarized vector mesons from the nucleon vanishes. This confirms the all-orders proof by Collins and Diehl. SPIRES or http://arXiv.org/abs/hep-ph/0108214 • Photoproduction of charmed vector mesons,$\gamma+N\to {\cal B}_c +\overline{D^*}$, with${\cal B}_c=\Lambda_c$or$\Sigma_c$Michail P. Rekalo and Egle Tomasi-Gustafsson The energy and the angular dependence of the associative vector charmed${D^*}$-meson photoproduction,$\gamma+N\to {\cal B}_c+ \overline{D^*}$, with${\cal B}_c=\Lambda_c$or$\Sigma_c$, has been predicted in framework of pseudoscalar D-meson exchange model. The behavior of the cross section is driven by phenomenological form factors, which can be parametrized in terms of two independent parameters. The predicted values of the cross section are sizeable enough to be measured in the near threshold region. SPIRES or http://arXiv.org/abs/hep-ph/0108237 • The Fadin-Lipatov-vertex in high-energy heavy quark and charmonium production Philipp Hagler Calculations of heavy quark and charmonium hadroproduction are presented in the k_t-factorization approach. The resulting differential cross sections are compared to experimental values and NLO collinear predictions. The application of the full effective Fadin-Lipatov quark-antiquark- production-vertex has an important influence on the results and in particular leads to a strong suppression of certain color octet contributions which are related to the outstanding problem of the production of polarized J/Psi. SPIRES or http://arXiv.org/abs/hep-ph/0109039 • Charmonium decays: J/psi --> e+e- and eta_c --> gamma gamma Andrzej Czarnecki and Kirill Melnikov We compute the O(alpha_s^2) correction to the decay rate eta_c --> gamma gamma and discuss its implications for precision quarkonium physics. We study the suitability of the ratio Gamma(J/psi --> e+e-)/Gamma(eta_c --> gamma gamma), in which the non-perturbative or soft effects cancel at O(alpha_s^{0,1}), for extracting fundamental parameters of QCD at low energies. We show that the QCD-based theory of charmonia is not capable of predicting this ratio with any degree of confidence. SPIRES or http://arXiv.org/abs/hep-ph/0109054 • Production of a pion pair in semileptonic decay of$J/\Psi$,$\Upsilon$and$B_c$J. P. Ma (ITP), Jia-Sheng Xu (CCAST & Itp) We study the semileptonic decay of$J/\Psi$,$\Upsilon$and$B_c$into two pions in the two kinematic regions. One is specified by that the two pions have large momenta, but have a small invariant mass. Another is specified by that the two pions have small momenta. In both cases we find that in the heavy quark limit the decay amplitude takes a factorized form, in which the nonperturbative effect related to heavy meson is represented by a NRQCD matrix element. The nonperturbative effects related to the two pions are represented by some universal functions characterizing the conversion of gluons into the pions. Using models for these universal functions and chiral perturbative theory we are able to obtain numerical predictions for the semileptonic decays into two pions. Our numerical results show that the semileptonic decay of$\jpsi$into two pions is at order of$10^{-5}with reasonable cuts and can be observed at BES II and the proposed BES III and CLEO-C. For other decays the branching ratio may be too small to be measured. SPIRES or http://arXiv.org/abs/hep-ph/0109055 • Vector meson masses in hot nuclear matter : the effect of quantum corrections Amruta Mishra, Jitendra C. Parikh, Walter Greiner The medium modification of vector meson masses is studied taking into account the quantum correction effects for the hot and dense hadronic matter. In the framework of Quantum Hadrodynamics, the quantum corrections from the baryon and scalar meson sectors were earlier computed using a nonperturbative variational approach through a realignment of the ground state with baryon-antibaryon and sigma meson condensates. The effect of such corrections was seen to lead to a softer equation of state giving rise to a lower value for the compressibility and, an increase in the in-medium baryonic masses than would be reached when such quantum effects are not taken into account. These quantum corrections arising from the scalar meson sector result in an increase in the masses of the vector mesons in the hot and dense matter, as compared to the situation when only the vacuum polarisation effects from the baryonic sector are taken into account. SPIRES or http://arXiv.org/abs/nucl-th/0108035 SPIRES or www • New predictions for inclusive heavy-quarkonium P-wave decays N. Brambilla, D. Eiras, A. Pineda, J. Soto, A. Vairo We show that some NRQCD colour-octet matrix elements can be written in terms of (derivatives of) wave functions at the origin and non-perturbative universal constants once the factorization between the soft and ultrasoft scale is achieved by using an effective field theory where only ultrasoft degrees of freedom are kept as dynamical entities. This allows us to derive a new set of relations between inclusive heavy-quarkonium P-wave decays into light hadrons with different principal quantum number and with different heavy flavour. In particular, we can estimate the branching ratios of bottomonium P-wave states by using charmonium data. SPIRES or http://arXiv.org/abs/hep-ph/0109130 •J/\psi$suppression in Pb+Pb collisions, a conventional description A. K. Chaudhuri (VECC, Calcutta) We have analyzed the latest NA50 data on$J/\psi$suppression in Pb + Pb collisions.$J/\psi$production is assumed to be a two step process, (i) formation of$c\bar{c}$pair, which is accurately calculable in QCD and (ii) formation of$J/\psi$meson from the$c\bar{c}$pair, which can be conveniently parameterized. In a pA/AA collision, the as the$c\bar{c}$pair pass through the nuclear medium, it gain relative square momentum at the rate of$\epsilon^2$per unit path length. As a result, some of the$c\bar{c}$pairs can gain enough momentum to cross the threshold to become an open charm meson, leading to suppression in pA/AA collisions. The parameters of the model were fixed from experimental data on the total$J/\psi$cross section as a function of effective nuclear length. The model without any free parameter, give excellent description of NA50 data on$E_T$dependence of$J/\psi$to Drell-Yan ratio. The model was applied to predict the$E_T$dependence of$J/\psi$at RHIC energy. Much larger suppression of$J/\psi$, in agreement with other model calculations are predicted. SPIRES or http://arXiv.org/abs/hep-ph/0109141 • Photoproduction of Heavy Quarkonia B. Jaeger (Inst. Theor. Physics, Univ. Regensburg) and W. Schweiger We investigate the reaction gamma+p -> V+p, with V denoting a Phi or a J/Psi meson, within the scope of perturbative QCD, treating the proton as a quark-diquark system. Our predictions extrapolate the existing forward differential cross-section data into the few-GeV momentum-transfer region. In case of the J/Psi reasonable results are only obtained by properly taking into account its mass in the perturbative calculation of the hard-scattering amplitude. SPIRES or http://arXiv.org/abs/hep-ph/0109144 • Diffractive charm photoproduction at HERA ep-collider A. V. Berezhnoy, V. V. Kiselev, I. A. Korzhavina, A. K. Likhoded The cross section of the$D^*$-meson diffractive photoproduction at the HERA collider has been calculated in the framework of perturbatively motivated model for the different kinematic regions. The camparison between the different Pomeron models has been performed. SPIRES or http://arXiv.org/abs/hep-ph/0109164 • On the intrinsic charm and the recombination mechanisms in charm hadron production J.C. Anjos, J. Magnin, G. Herrera We study$\Lambda_c^\pm$production in$pN$and$\pi^-N$interactions. Recent experimental data from the SELEX and E791 Collaborations at FNAL provide important information on the production mechanism of charm hadrons. In particular, the production of the$\Lambda_c$baryon provides a good test of the intrinsic charm and the recombination mechanisms, which have been proposed to explain the so called leading particle effects. SPIRES or http://arXiv.org/abs/hep-ph/0109185 • Aspects of Charmonium Physics S.F. Tuan I review possible resolution of the$J/\psi (\psi^{\prime}) \to \rho-\pi$puzzle based on two inputs: the relative phase between the one- photon and the gluonic decay amplitudes, and a possible hadronic excess in the inclusive nonelectromagnetic decay rate of$\psi^{\prime}$. The status of a universal large phase here is examined for its meaning and implications (including those for B-physics). Since the future of tau/charm facility(s) are again under consideration together with a future anti-proton facility at GSI, I propose to extend my review to include a broader discussion of charmonium physics. Outstanding questions like the status of the$^{1}P_{1}$state of charmonium, measuring$D^{0}-\bar D^{0}$mixing and relative strong phases, status of molecular P(S) - wave charmonia will also be discussed amongst others. SPIRES or http://arXiv.org/abs/hep-ph/0109187 • Heavy Flavour Physics at HERA - a Survey P. J. Bussey At the HERA collider at DESY, high energy electron and positron beams interact with proton beams. A review is presented of the variety of ways in which these collisions produce final states containing charm and beauty quarks. SPIRES or http://arXiv.org/abs/hep-ph/0109254 • Intrinsic Charm Flavor and Helicity Content in the Proton Xiaotong Song (Univ. of Virginia) Contributions to the quark flavor and spin observables from the intrinsic charm in the proton are discussed in the SU(4) quark meson fluctuation model. Result suggests that the probability of finding the intrinsic charm in the proton is less than 1%. The intrinsic charm helicity is small and negative,$\Delta c \simeq -(0.003\sim 0.015)$. The fraction of the total quark helicity carried by the intrinsic charm is less than 2%. A detail comparison of the quark flavor and spin observables with data and other models or analyses is given. SPIRES or http://arXiv.org/abs/hep-ph/0109289 • Relative phase between the three-gluon and one-photon amplitudes of the J/psi decays N.N. Achasov (Sobolev Institute for Mathematics SB RAS, Novosibirsk) It is shown that the study of the \omega-\rho interference pattern in the J/psi -> (rho+omega)eta -> pi+pi-eta decay provides evidence for the large (nearly 90 degrees) relative phase between the isovector one-photon and three-gluon decay amplitudes. SPIRES or http://arXiv.org/abs/hep-ph/0110057 • Dissociation of a Heavy Quarkonium at High Temperatures Cheuk-Yin Wong (ORNL) We examine three different ways a heavy quarkonium can dissociate at high temperatures. The heavy quarkonium can dissociate spontaneously when it becomes unbound at a temperature above its dissociation temperature. Following the recent work of Digal, Petreczsy, and Satz, we calculate the dissociation temperatures of heavy quarkonia taking into account the angular momentum selection rules and using a temperature-dependent potential inferred from lattice gauge calculations. We find that the selection rules change the dissociation temperatures substantially for charmonia but only slightly for bottomia. A quarkonium system in thermal equilibrium with the medium can dissociate by evaporation. The fraction of quarkonium lying above the dissociation threshold increases as temperature increases. A quarkonium can also dissociate by colliding with light hadrons. We evaluate the cross sections for the dissociation of J/psi and Upsilon in collision with pion as a function of the temperature of the hadron medium, using the quark-interchange model of Barnes and Swanson. We find that as the temperature increases, the threshold energy decreases and the dissociation cross section increases. SPIRES or http://arXiv.org/abs/nucl-th/0110004 • Non-perturbative gluons in diffractive photo-production of J/Psi M. B. Gay Ducati, Werner K. Sauter The modifications induced in the calculation of the cross section of the diffractive process gamma gamma -> J/Psi J/Psi when the gluon propagator is changed are analyzed. Instead of the usual perturbative gluon propagator, alternative forms obtained using non-perturbative methods like Dyson-Schwinger equations are used to consider in a more consistent way the contributions of the infrared region. The result shows a reduction in the differential cross-section for low momentum transfer once compared with the perturbative result, to be confirmed with future experimental results from TESLA. SPIRES or http://arXiv.org/abs/hep-ph/0110162 • Parity and Time Reversal in J/Psi Decay L. Clavelli, T. Gajdosik, and I. Perevalova (University of Alabama) With the prospect of large numbers of J/Psi decay events becoming available in the near future, it is interesting to search for symmetry violating effects as probes of new physics and tests of the standard model. J/Psi decay events could provide the first observation of weak effects in otherwise strongly decaying particles. We calculate a T odd asymmetry in the J/Psi decay into photon plus lepton pair due to Z boson exchange. Extensions to hadronic final states are also discussed. SPIRES or http://arXiv.org/abs/hep-ph/0110076 • Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction J.L. Domenech-Garret, M.A. Sanchis-Lozano and S. Wolf (Valencia We examine carefully bottomonia hadroproduction in proton colliders, especially focusing on the LHC, as a way of probing the gluon density in protons. To this end we develop some previous work, getting quantitative predictions and concluding that our proposal can be useful to perform consistency checks of the parameterization sets of different parton distribution functions. SPIRES or http://arXiv.org/abs/hep-ph/0110085 • The charm quark's mass in quenched QCD Juri Rolf, Stefan Sint We present our preliminary result for the charmed quark mass, which follows from taking the D_s and K meson masses from experiment and r0=0.5 fm (or, equivalently F_K=160 MeV) to set the scale. For the renormalization group invariant quark mass we obtain M_c = 1684(64) MeV, which translates to m_c(m_c)= 1314 (40)(20)(7) MeV for the running mass in the MSbar scheme. Renormalization is treated non-perturbatively, and the continuum limit has been taken, so that the only uncontrolled systematic error consists in the use of the quenched approximation. SPIRES or http://arXiv.org/abs/hep-ph/0110139 • Next-to-leading-log renormalization-group running in heavy-quarkonium creation and annihilation Antonio Pineda In the framework of potential NRQCD, we obtain the next-to-leading-log renormalization-group running of the matching coefficients for the heavy quarkonium production currents near threshold. This allows to obtain S-wave heavy-quarkonium production/annihilation observables with next-to-leading-log accuracy within perturbative QCD. In particular, we give expressions for the decays of heavy quarkonium to e^+e^- and to two photons. SPIRES or http://arXiv.org/abs/hep-ph/0110216 • Momentum Transfer Dependence of the Differential Cross Section for$J/\psi$Production E. Gotsman (Tel-Aviv U.), E. Levin (Tel-Aviv U.), U. Maor (Tel-Aviv We discuss the$\abst$dependence of$J/\psi$production in the region of$0<\abst\lsim M^2_{\psi}$. The forward slope of the elastic differential cross section is calculated assuming a dipole-type dependence for the gluon ladder-proton form factor. The$\abst$dependence of$d\sigma/dt$is obtained using DGLAP evolution both for the elastic channel at low$\abst$and for the inelastic channel at large values of$\abst$, up to$\abst\simeq M^2_{\psi}$. Results are presented and compared with the relevant experimental data. SPIRES or http://arXiv.org/abs/hep-ph/0110256 • Gluonic effects in vector meson photoproduction at large momentum transfers N.I.Kochelev and V.Vento The gluonic pole has been instrumental in explaining the mass of the$\eta^{\prime}$and providing a plausible explanation for solving the spin crisis. We show that it also plays an important role in the description of the photoproduction of vector mesons at high momentum transfers at JLab energies. SPIRES or http://arXiv.org/abs/hep-ph/0110268 • J/psi Enhancement in Peripheral Pb+Pb Collisions at SPS A.P. Kostyuk, M.I. Gorenstein, H. Stoecker, and W. Greiner Production of J/psi-mesons in heavy ion collisions is considered within the statistical coalescence model. The charmed quark-antiquark pairs are assumed to be created at the initial stage of the reaction and their number is conserved during the evolution of the system. At the hadronization stage, the charmed (anti)quarks are distributed among open and hidden charm hadrons in accordance with the prescriptions of the statistical mechanics. The model is in excellent agreement with the experimental data for Pb+Pb collisions in a wide centrality range, including the so called "anomalous" suppression domain. For the peripheral collisions, however, the model predicts enhanced J/psi production with respect to the "normal" nuclear suppression curve. SPIRES or http://arXiv.org/abs/hep-ph/0110269 • Leptoproduction of Polarized Vector Mesons B. Postler (Wuppertal Univ.) We present a status report on a study of vector meson leptoproduction for the HERA energy range on the basis of the generalized handbag approach. In contrast to the leading twist approach transverse degrees of freedom as well as Sudakov suppressions are taken into account in the subprocess. First results for the cross section for photoproduction of longitudinally polarized rho-mesons are found to be in fair agreement with experiment. SPIRES or http://arXiv.org/abs/hep-ph/0110271 • Heavy quark production at HERA in k_t factorization supplemented with CCFM evolution H. Jung (Physics Department, Lund University, Sweden) The application of k_t - factorization, supplemented with the CCFM small-x evolution equation, to heavy quark production is discussed. Differential cross sections of b-b_bar production and also inelastic J/psi production as measured at HERA are compared to the hadron level CCFM Monte Carlo generator CASCADE, using the unintegrated gluon density obtained within the CCFM evolution approach from a fit to HERA F_2 data. SPIRES or http://arXiv.org/abs/hep-ph/0110345 • Renormalization group improvement of the NRQCD Lagrangian and heavy quarkonium spectrum Antonio Pineda We complete the leading-log renormalization group scaling of the NRQCD Lagrangian at$O(1/m^2)$. The next-to-next-to-leading-log renormalization group scaling of the potential NRQCD Lagrangian (as far as the singlet is concerned) is also obtained in the situation$m\alpha_s \gg \Lambda_{QCD}$. As a by-product, we obtain the heavy quarkonium spectrum with the same accuracy in the situation$m\alpha_s^2 \simg \Lambda_{QCD}$. When$\Lambda_{QCD} \ll m\alpha_s^2$, this is equivalent to obtain the whole set of$O(m\alpha_s^{(n+4)} \ln^n \alpha_s)$terms in the heavy quarkonium spectrum. The implications of our results in the non-perturbative situation$m\alpha_s \sim \Lambda_{QCD}$are also mentioned. SPIRES or http://arXiv.org/abs/hep-ph/0109117 • Discovery potential for New Physics in view of the RHIC-Spin upgrade P. Taxil and J.-M. Virey In view of a possible upgrade of the RHIC-Spin program at BNL, concerning both the machine and the detectors, we give some predictions concerning the potentialities of New Physics detection with polarized proton beams. We focus on parity-violating asymmetries in one-jet production due to contact terms or to a new leptophobic neutral gauge boson. We comment on the main uncertainties and we compare with unpolarized searches at Tevatron. SPIRES or http://arXiv.org/abs/hep-ph/0109094 • A Variational Fock-Space Treatment of Quarkonium L. Di Leo and J. W. Darewych (York University, Toronto, Canada) The variational method and the Hamiltonian formalism of QCD are used to derive relativistic, momentum space integral equations for a quark-antiquark system with an arbitrary number of gluons present. As a first step, the resulting infinite chain of coupled equations is solved in the nonrelativistic limit by an approximate decoupling method. Comparison with experiment allows us to fix the quark mass and coupling constant, allowing for the calculation of the spectra of massive systems such as charmonium and bottomonium. Studying the results with and without the nonAbelian terms, we find that the presence of the nonAbelian factors yields better agreement with the experimental spectra. SPIRES or http://arXiv.org/abs/hep-ph/0010127 • Power counting and effective field theory for charmonium Sean Fleming (1), Adam K. Leibovich (2) and I. Z. Rothstein (1) ((1) We hypothesize that the correct power counting for charmonia is in the parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as is HQET). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of NRQCD. In particular, we show that while Lambda_QCD/m_c power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include: A hierarchy between spin singlet and triplet octet matrix elements in the J/psi system. A quenching of the net polarization in production at large transverse momentum. No end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD. SPIRES or http://arXiv.org/abs/hep-ph/0012062 • Integral characteristics of bremsstrahlung and pair photoproduction in a medium V. N. Baier and V. M. Katkov The bremsstrahlung of an electron and$e^{-}e^{+}\$-pair creation by a photon in a medium is considered in high-energy region, where influence of the multiple scattering on the processes (the Landau-Pomeranchuk-Migdal (LPM) effect) becomes essential. The integral characteristics: the radiation length and the total probability of radiation and pair photoproduction are analyzed under influence of the LPM effect.
SPIRES or http://arXiv.org/abs/hep-ph/0012064