V_(ub) from exclusive semileptonic B - ρ decays

摘要

We use Omnès representations of the form factors V, A_1 and A_2 for exclusive semileptonic B->p decays, and apply them to combine experimental partial branching fraction information with theoretical calculations of the three form factors to extract V_(ub). We find V_(ub) = (2.8 ± 0.2_(stat) ± 0.5_(sys)) × 10~(-3), where we have conservatively assumed a 20 systematic error to account for the use of the quenched approximation in the lattice QCD calculations of the form factors. This value of V_(ub) is slightly lower than the values extracted from exclusive semileptonic B -> π decays, (3.47 ± 0.29 ± 0.03) × 10~(-3) J.M. Flynn, J. Nieves, Phys. Rev. D 76 (2007) 031302, (3.36 ± 0.23) × 10~(-3) C. Bourrely, I. Caprini, L. Lellouch, Phys. Rev. D 79 (2009) 013008, (3.38 ± 0.35) × 10~(-3) J. Bailey, et al., arXiv:0811.3640 hep-lat, and using all other inputs in CKM fits, (3.55 ± 0.15) × 1O~(-3) UTfit Collaboration M. Bona, et al., JHEP 0610 (2006) 081, hep-ph/0606167; UTfit Collaboration, http://utfit.romal.infn.it/ckm-results/ckm-results.html.The disagreement is greater when we compare to the result extracted from inclusive B->X_ulv decays, V_(ub) = (4.10 ± 0.30_(exp) ± 0.29_(th)) × 10~(-3) M. Neubert, in: Proceedings of FPCP 2007: 5th Conference on Flavor Physics and CP Violation, Bled, Slovenia, 12-16 May 2007 (2007).