Questions for participating theorists


|Vub| and b->sg questions

1.      Please list a set of measurements that would, when combined, result in the most precise and reliable determination of |Vub| with the current available data.

2.      What are the best ways of determining the uncertainty on |Vub| due to the HQE and SF? How big are these uncertainties and what is their source?  What other sources of uncertainty on |Vub| need to be considered?

3.      The inclusive endpoint spectrum for b->ulnu decays has now been measured down to 2.0 GeV. How important would it be to reduce still further the Ee cut?  How does this lower Ee cut impact the extraction of Vub from the ratio of integrals of the  lepton spectrum from b-> u l nu and the photon spectrum from b-> s gamma?  Assuming we can measure the full Ee spectrum, can we extract the leading SF in b->ulnu decays?

4.      Can the shape function moments for b->sg and/or b->ulnu be predicted from HQE parameters determined in b->clnu decays? If not, what prevents this? If the predicted moments match the data, can we use the b->clnu parameters in determinations of |Vub|?

5.      Is there consensus on the necessity of "bias corrections" to b->sg moments (for Ecut in the range 1.8 to 2.0 GeV)?

6.      How big are the leading uncertainties in the BF and moments for b->sg and what is their source?

7.      Despite its known shortcomings, we still use the DeFazio-Neubert model (order alpha_s triple differential decay rate convoluted with a SF ansatz) to model our data in the Mx, q2-Mx, Ee and q2-Ee. We do this because we need to construct a realistic Monte Carlo generator with which to evaluate our experimental efficiencies. Are there viable alternative approaches? How would you quantify the theoretical uncertainty associated with this approach? Same questions regarding the use of the Kagan-Neubert model for b->sg.

HQE questions

8.      The experimental determination of spectral moments in semileptonic and radiative B decays will continue to improve. What improvements are needed in the calculations to keep pace? Which uncertainties do we not know how to reduce?

SF questions

9.      How can the uncertainties associated with sub-leading SFs be quantified? Where could we expect to see an experimental indication of the importance of sub-leading SFs?

SCET questions

10.  What can we expect from SCET? What are the most pressing issues (conceptual and/or practical) to resolve in the near term? How can we probe SCET experimentally?

Other questions

11.  For which processes (b->clnu, b->ulnu, b->sg ) is it most useful to have separate measurements for B0 and B+, taking account of the reduced experiment accuracy available in these tagged measurements? How can we use these measurements to quantify uncertainties due to Weak Annihilation?

12.  Quark-hadron duality: how can we probe its region of validity? How should we treat the regions (e.g. at low hadron mass in b->sg or b->ulnu) where it clearly breaks down? How would you assign an uncertainty?