Working Group 6: B Decay Models

- questions - the book - workshop agenda - monte carlo -

Theorist Conveners: Ikaros Bigi, Daniel Wyler

Experimentalist Conveners: Patricia Rankin, Roland Waldi

This group aims at a critical review of the status of B decays and the models, parameters and ideas that characterize them, based on latest data and calculations.
  • A tested theoretical description is required in extracting reliable numerical values for CKM parameters |V(cb)|, |V(ub)| and |V(td)| from data.
  • Likewise a good theoretical or at least phenomenological treatment is needed for a reliable numerical interpretation of future measurements of CP asymmetries in B decays
  • Novel lessons on QCD at the interface between perturbative and non-perturbative dynamics can be learnt.
    •

    List of Questions

    1. Semileptonic B Decays

    covered almost exhaustively by group 4
  • Which models describe the lepton spectrum of present data?
  • heavy quark expansion for inclusive semileptonic decays
  • bound quark models: in which way can ACCMM be improved?
  • form factor models: which are favoured by data? what are the best parameters? (this topic is also of interest to group 12d/Tagging)
    •
  • What is known on BR(B -> tau nu X), what can we learn at BABAR?
  • Which models describe best the dominant exclusive b -> c decays (D l nu, D* l nu, ...)?
  • form factors, HQET and the Isgur Wise function: what is known, what can be learnt from BABAR?
    •
  • Which models describe best the dominant exclusive b -> u decays (pi l nu, rho l nu, eta l nu, omega l nu, ...)?
  • What is known on higher resonances, which feed down into rho l nu, pi l nu...?
    •  Downloadable References:
    1. a review by Pat Burchat and Jeff Richman, Rev.Mod.Phys.67:893-976,1995.
    2. a theoretical review by Patrick J. O'Donnell and Gürsevil Turan, UTPT-96-06.
    3. a recent thesis by Lev A. Koyrakh, HEPPH-9607443 (1996).

      Lepton Spectra

    4. I.I. Bigi, M. Shifman, N.G. Uraltsev, A.I. Vainshtein, Phys.Rev.Lett. 71 (1993) 496.
    5. B. Blok, L. Koyrakh, M. Shifman, A.I. Vainshtein, Phys.Rev.D49 (1994) 3356.
    6. I.I. Bigi, M. Shifman, N.G. Uraltsev, A.I. Vainshtein, Phys.Rev.D52 (1995) 196.
    7. N.G. Uraltsev, preprint hep-ph/9612349.
    8. I.I. Bigi, N.G. Uraltsev, Nucl.Phys. B423 (1994) 33.

    2. Inclusive and Exclusive Hadronic Decays

    2.1 Inclusive properties

  • What is the total hadronic width?
  • Review b semileptonic branching ratio and charm counting problem.
  • Inputs on n_c from experiment/BABAR: inclusive data (charmed hadron multiplicities) and (semi-)exclusive data (like D anti-D K).
  • What is the ratio of B+/B0 lifetimes?
    (this topic is also of interest to group 7)
    •
  • How are inclusive B decays described?
  • spectator and non-spectator graphs: what is known? what can we learn?
  • what are the parameters (c1, c2, ...)?
  • general QCD models: ideas and predictive power?
  • how much do penguins contribute (b -> s g)?
  • how are baryons produced in B decays?
    •
  • Inclusive properties of B decays:
  • multiplicities of charged particles, photons, pions, kaons, protons, Lambdas...?
  • inclusive spectra of stable final particles?

    The following topics are also of interest to group 12/Tagging:

  • charge-flavour correlations of kaons, pions, protons? what could be discriminating variables to increase these correlations?
  • strangeness-flavour correlations (K, Lambda)?
  • D meson properties: spectra, flavour correlation (how much D mesons are from W -> D X)?
  • D_s meson properties: spectra, flavour correlation (how much D_s mesons are from b -> c)?
    •
    • Downloadable References:
    1. reviews by Thomas Browder and Klaus Honscheid, Prog.Part.Nucl.Phys. 35:81-220,1995; and together with Daniele Pedrini, UH-515-848-96

      spectator effects:

    2. M. Neubert, C.T. Sachrajda, preprint

    2.2 B Decays to Mesons

  • What are the ideas in tree diagram spectator models?
  • Factorization (two-body, multi-body)
  • Colour suppression
  • Form factors and decay constants
  • How big are annihilation and W-exchange contributions?
  • How big is Pauli interference?
  • How big are penguin contributions?
    (this topic is also of interest to group 12 for CP-asymmetric final states)
  • how important are final state interactions? what do we know on rescattering?
    •
  • Two-body decays:
  • Do factorization and form factor models work?
  • Are the effective colour coefficients a1, a2 universal?
  • What are the branching ratios (from experiment/theory)?
  • DEFAULT BRs FOR ALL WORKING GROUPS
    •
  • Three-body decays:
  • How big is the non-resonant fraction (true 3-body)?
  • Which theoretical models can describe those?
    •

    • 2.3 B Decays to Baryons

  • What theoretical models do exist?
  • What are the branching ratios (from experiment/theory)?
    •

    3. Models for Rare B Decays

    This topic is discussed in group 5 and transverse theory groups.

    Downloadable References:

    1. B -> X_s photon:
    2. M. Neubert, Phys.Rev.D? (1994) 4623.

    4. Theory for (1)-(3)

    Theoretical models span topics (1)-(3) and cross all working groups. Therefore, they are combined according to theoretical models as transverse groups.

    5. Optimization of Monte Carlo Event Generators

    The knowledge from experiment and theory should be optimally combined in our Monte Carlo Event Generators.

    6. Relevant Parameters of B Mesons

  • B meson masses
  • B+, B0 and B_s meson lifetimes (review and BABAR measurements) will be covered by group 7,
  • B_sL - B_sS lifetime difference (theoretical review and BABAR measurements) will be covered by group 7,
  • B0 and B_s meson oscillation (review and BABAR measurements) will be covered by group 7,
  • B decay parameters f_B, f_{B_s}, B_B:
    will be covered by group 7 and and will be reviewed by transverse theory groups on lattice gauge theory and QCD sum rules. Determination at BABAR (B -> tau nu) is discussed at group 5).
    •  Downloadable References:
    Masses, lifetimes and branching ratios from the Particle Data Group 1996 index.
    a side-topic:

    7. Parameters of the Upsilon(4S)

    While Upsilon spectroscopy is not a subject of BABAR studies, the Upsilon(4S) properties are accessed anyway, and BABAR may contribute to the determination of
  • the Y(4S) mass
  • the Y(4S) total width and Gamma_ee
  • the Y(4S) branching fractions
    •  This topic is also of interest to group 7

    7.1 EPR correlations in Upsilon(4S) -> B0 anti-B0

    A test of quantum mechanics

    Preliminary outline for The Book

    contributions:
  • B Decay Theory
  • Exclusive Hadronic B Decays
  • From the OPE to BSW (A.Petrov,D.Wyler)
  • Factorization (A.Petrov,Y.Y.Keum,D.Wyler)
  • Final state interactions (A.Petrov,P.Colangelo,D.Wyler)
    •
  • Multibody Decays
  • Hadronic Couplings (D.Wyler)
  • HQ chiral perturbation theory (I.Bigi)
  • Factorization in Multibody Decays (I.Bigi)
  • Hadronic Penguins (D.Wyler)
    •
  • Baryon Production (I.Bigi)
    •
  • B Decays: Status of Experimental Information
  • Exclusive Decays (P.Rankin)
  • b -> c
  • b -> u
  • b -> s
    •
  • Inclusive Decays (R.Waldi)
  • B Decays to Baryons (R.Waldi)
    •
  • Upsilon(4S) Decays
  • Upsilon(4S) resonance parameters, cross section
  • Upsilon(4S) -> B anti-B photon (P.Colangelo)
  • The EPR paradoxon in Upsilon(4S) -> B anti-B (H.Lipkin,I.Bigi)
    •
    • other topics related to this chapter:
  • general: Introduction (A.Falk)
  • WG 7: Operator Product Expansion and Inclusive Decay Properties
  • WG 4+7: HQET and Heavy Quark Expansion
  • WG 7: Charmless Decay Fraction (I.Dunietz,H.Lipkin)
  • appendix: Lattice Gauge Theory (Sachrajda)
  • appendix: Sum Rules (Khodjamirian,Ball,Colangelo,Paver)
    •

    Agenda for the next Workshop

    not yet planned

    ...And More

    DEFAULT BRs FOR ALL WORKING GROUPS

    A list of references as postscript or TeX source.

    Recent general theoretical reviews:
    I.L. Grach et al., INFN-ISS-95-17.
    G.Martinelli, ROME-1155-1996.

    back to the Physics Workshops homepage

    comments or contributions welcome: just send email to all conveners, Tricia, Daniel, Ikaros, Roland or use the hypernet BABAR Discussion group 6.

    Last update: 23 June 97, RW.