A Study of Exclusive Charmless Semileptonic B Decays and Extraction of |V_{ub}| at CLEO

TL;DR

This paper measures exclusive charmless semileptonic B decay branching fractions and extracts the CKM matrix element |V_{ub}| using data from the CLEO experiment, reducing model dependence through phase space analysis.

Contribution

It provides new measurements of branching fractions for B to pi, rho, eta, eta' decays and determines |V_{ub}| with combined experimental and theoretical uncertainties.

Findings

Branching fraction B(B^0 -> pi^-l^+nu) = (1.37 +- 0.15 +- 0.11) x 10^-4

Branching fraction B(B^0 -> rho^- l^+ nu) = (2.93 +- 0.37 +- 0.37) x 10^-4

Estimated |V_ub| = (3.6 +- 0.4 +- 0.2 +0.6 -0.4) x 10^-3

Abstract

We have studied semileptonic B decay to the exclusive charmless states pi, rho/omega, eta and eta' using the full 15.5 fb^-1 CLEO Upsilon(4S) sample, with measurements performed in subregions of phase space to minimize dependence on a priori knowledge of the form factors involved. We find total branching fractions B(B^0 -> pi^-l^+nu) = (1.37 +- 0.15_stat +- 0.11_sys) x 10^-4 and B(B^0 -> rho^- l^+ nu) = (2.93 +- 0.37_stat +- 0.37_sys) x 10^-4. We find evidence for B^+ -> eta' l^+ nu, with B(B^+ -> eta' l^+ nu) = (2.66 +- 0.80_stat +- 0.56_sys) x 10^-4 and 1.20 x 10^-4 < B(B^+ -> eta' l^+ nu) < 4.46 x 10^-4 (90% CL). We also limit B(B^+ -> eta l^+ nu) < 1.01 x 10^-4 (90% CL). By combining our B -> pi l nu information with unquenched lattice calculations, we find |V_ub| = (3.6 +- 0.4 +- 0.2 +0.6 -0.4) x 10^-3, where the errors are statistical, experimental systematic, and theoretical systematic, respectively.