|Vub| from exclusive semileptonic B→ρ decays

We use Omnès representations of the form factors V, A1 and A2 for exclusive semileptonic B→ρ decays, and apply them to combine experimental partial branching fraction information with theoretical calculations of the three form factors to extract |Vub|. We find |Vub|=(2.8±0.2stat±0.5sys)×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 |Vub| 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)×10−3 [UTfit Collaboration M. Bona, et al., JHEP 0610 (2006) 081, hep-ph/0606167; UTfit Collaboration, http://utfit.roma1.infn.it/ckm-results/ckm-results.html]. The disagreement is greater when we compare to the result extracted from inclusive B→Xulν decays, |Vub|=(4.10±0.30exp±0.29th)×10−3 [M. Neubert, in: Proceedings of FPCP 2007: 5th Conference on Flavor Physics and CP Violation, Bled, Slovenia, 12-16 May 2007 (2007)].