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= List of Questions for SLAC Lattice Workshop =
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*** Semileptonic B -> X_c l nu ***
For theory:
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1. Does lattice theory obey the constraints derived from dispersion relations
and/or sum rules?
2. Can lattice shed any light beyond point at Q2=Q2Max (w=1)? E.g., value of
rhosq? R1(w) or R2(w) dependence?
3. Is lattice theory right? E.g., QED confined on lattice, etc. Are there any
clean test?
4. Can form-factors light mesons at large Q2 (~10.6^2) shed any light on
validity of calculations (latice or whatever) in the B-sector?
5. Dispersion relation (e.g., CLN) and sum rule (Oliver et. al) yield virtual
identical w-dependence for ISF (hA1) when value of rhosq (=d\xi/dw)
near measured value is used, but differ if rhosq far off. Is there a
prediction of rhosq implicit in the consistency of these different
approaches? If so can lattice shed any light on the subject?
6. How do s.l. FF relate to FF for b to s gamma?
*** Semileptonic B -> X_u l nu ***
For theory:
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1. A large portion of our B->pi(rho...)lnu data lies at q^2<16 GeV^2,
i.e. in the region where lattice results don't exist. In addition, the
measurement at high q^2 has somewhat larger exp. uncertainties
mainly due to cross-feed from other B->Xulnu decays. It would thus
be nice if we could use the whole q^2 spectrum for the extraction
of |Vub| instead of only a very restricted range.
- How can we connect the predictions of the form-factor normalization
for high-q^2 (LQCD) and low-q^2 (LCSR) to make best use of our
experimental data.
- What are the prospects for lattice to calculate points at lower q^2?
- The form-factor shape is now determined quite precisely from
experiments. This allows also a test of different form-factor
calculations. In order to get a precise prediction for the
normalization, would it make sense that lattice concentrates
on calculating only one (or a few) points (preferably in the intermediate
q^2 range) with much better statistical precision?
2. What are the prospects for reduction of the systematic uncertainties
of the lattice results?
3. What can we expect from lattice for other pseudoscalar (eta, eta')
and vector (rho, omega) mesons? Is the omega more promising than
the rho due to its smaller width?
Why is B->pilnu easier to compute on the lattice than the other
exclusive B->Xulnu decays?
4. For vector mesons, we need to perform a full 4-dim fit (including three
decay angles) to measure the form factor shapes. We will not have
enough statistics to do this in the near future. Are there any
relations between the shapes of the different form factors that
allow us e.g. to measure ratios and reduce the number of parameters?
Can any of the form factors be assumed approximately constant?
5. What can SCET tell us from B to pi pi ?
6. Can the semileptonic FF measurements be useful to understand other
types of decays? Which? How?
7. HFAG provides Vub results for two unquenched LQCD FF calculations
(HPQCD & FNAL) and one quenched LQCD FF calculation (APE).
Which part of the Lattice errors between these FF calculations are
correlated? How large are the uncorrelated and correlated errors?
Taking these correlations into account, how consistent are the results?
For BaBar:
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1. How should lattice and experiment compare form factor shapes?
*** Semileptonic D decays ***
For theory:
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1. Are you expecting same or different hadronic form factors in:
D0 --> K- e+ nu and Ds --> eta/eta' e+ nu ? Distinguish between the
q2 dependence and the normalisation.
2. Same question for the vector form factor in Ds --> phi e nu:
why its q2 dependence can be different from the one measured
in D --> K e nu?
3. What are the expectations for the difference between form factors
(normalisation and q2 variation) in the D --> K* e nu and Ds --> phi e nu
channels? In several papers it is mentionned that it can be 10% (on
normalization?) what is the origin of this number?
4. What are we gaining in measuring Lc --> Lambda e nu form factors as
compared with mesons? Is this of interest for LQCD? (or other hadronic
approaches)? If yes, are there other semileptonic charm-baryon decay
channels of interest to measure?
5. What is the interest in having a new measurement of the total D*+ width?
6. The differential decay rates for B--> pi e nu and D --> pi e nu can be
related when considering pions emitted at the same w in the two channels.
Suppose that Vcd is known with infinite accuracy what is the ultimate
accuracy (from theory alone) you can expect for Vub in this approach?
7. How to treat sl radiative events?
At present the sl differential decay width is expressed as a function
of q^2. To simplify the discussion, consider that a single form factor is
contributing. How to fit the data as we do not separate radiative and
non_radiative events?
Simulated events have been generated using PHOTOS so if we know what q2
value has been used inside PHOTOS (or prior calling PHOTOS) when the form
factor dependence of the decay rate is used, it is easy to fit the
measurements by weighting events.
This approach suppose that one is satisfied with the generation of
photons in sl D decays using PHOTOS? How can we quantify the uncertainties
attached to this approach?
*** Leptonic ***
For theory:
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1. Is there anything we should be looking for/measuring that we currently
are not?
2. How much can you improve f_B and f_Ds and how well do you need us to
measure them?
3. On what timescale can we expect updated measurements of f_M?
For BaBar:
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1. What are the prospects for the leptonic decay rate of the B.
How do the BaBar and Belle results compare.
*** Radiative ***
For theory:
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1. Can lattice QCD calculate the ratio of (and also the individual) form
factors T1(B->K*)/T1(B->rho) and if so, what precision can be achieved.
Related to that, is there a new program to calculate the ratio of (and
also the individual) longitudinal to transverse decay constants for K*
and rho?
2. Can lattice QCD reliably estimate the u-quark contribution to the
B -> rho gamma decay (annihilation diagram and u-quark loop)?
3. In the light of Super B factories, is the inclusive ratio of
b->dgamma/b->sgamma easier to understand theoretically?
4. Since we are entering precision measurement of asymmetries (CP, isospin)
in the B -> K* gamma decays, can lattice QCD say anything about these
quantities?
5. How about the ratio of form factors for Bs->K* gamma / Bs-> phi gamma?
Could this be calculated in principle better than B -> rho gamma / B ->
K* gamma?
6. Is it possible to have a theoretically precise estimator of Vts/Vub by
measuring ratio of branching fractions B->Kll/B->pilnu at high q^2?
7. Are SU(3) breaking in the form factors more or less manageable than for
the vector meson case (K*/rho )?
*** Spectroscopy ***
For theory:
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1. Much better calculations of the masses of low-lying
four quark ($Q\bar{q}q\bar{Q}$) states are needed.
What is the prospect obtaining them in the near future.
Could a more indirect approach be used to decide if any
of the diquark combinations are sufficiently attractive to bind?
2. The combination of the static energy for hybrids and the SE for
obtaining the masses is very practical. If the Y(4260) is a hybrid
state, then there is a triplet of nearby states expected
(0-+, 1-+, 2-+). The splitting comes from including the heavy quark
spin fine structure. How could this be calculated? Even the sign
would be useful.
For BaBar:
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1. Mussa gives a list of suggestions for further tests for X,Y,Z states -
what are BaBar's comments on their feasiblilty?
2. The measurement of the $D^0\bar D^0 \pi^0$ decay mode of the X(3872)
by Belle is very important and somewhat problematic for the
molecular interpretation of the X. What can BaBar do here?
3. The Y(4260) and/or Y(4350) are above threshold for decays to D(*) D_P
states. These various decays play an important role in understanding
the nature of these states. What limit can you put on the ratio of
such decays to the $\pi \pi J/\psi (')$ discovery modes.