Experimental HEP Seminar

Measurement of |V_ub| from the decay B₀→π l ν, using a loose neutrino reconstruction technique, at BaBar

David Côté

Université de Montréal

We report the results of a study of the exclusive charmless semileptonic decay, B₀→π l ν, undertaken with approximately 227 million BB pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain model-independent partial branching fractions in 12 bins of q2, the momentum transfer squared, from which we extract the f+(q2) form-factor shape parameters: α_BK = 0.52±0.05±0.03, |Vubf+(0)| = (9.6±0.3±0.2)×10^-4, and the total branching fraction: BF(B₀→π l ν) = (1.46±0.07±0.08)×10^-4, hence obtaining the current most precise values of these parameters. Based on a recent theoretical calculation of the form factor in the range q2 > 16 GeV², we find the magnitude of the CKM matrix element V_ub to be (4.1±0.2±0.2 +0.6-0.4)x10^-4, where the last uncertainty is due to the normalization of the form factor.