Measurement of exclusive B to Xu l nu decays using full-reconstruction tagging at Belle

TL;DR

This paper measures branching fractions of exclusive charmless semileptonic B decays using full-reconstruction tagging at Belle, providing insights into |Vub| and testing theoretical form factor models with a large data sample.

Contribution

It presents the first precise measurements of several exclusive B to X_u l nu decay modes using full-reconstruction tagging at Belle, and extracts |Vub| with multiple theoretical form factor inputs.

Findings

Branching fractions for B to pi, rho, and omega modes are measured.

|Vub| is extracted with consistency across different q2 regions and theoretical models.

Results are based on 657 million BBbar pairs collected at Belle.

Abstract

We report on a study of the branching fractions for the exclusive charmless semileptonic B decay modes B to pi+ l nu, B to pi0 l nu, B to rho+ l nu, B to rho0 l nu and B to omega l nu, using events tagged by fully reconstructing one of the B mesons in a hadronic decay mode. The obtained branching fractions are B(B to pi+ l nu) = (1.12 +- 0.18 +- 0.05) x 1E-4, B(B to pi0 l nu) = (0.66 +- 0.12 +- 0.03) x 1E-4, B(B to rho+ l nu) = (2.56 +- 0.46 +- 0.12) x 1E-4, B(B to rho0 l nu) = (1.80 +- 0.23 +- 0.07) x 1E-4 and B(B to omega l nu) = (1.19 +- 0.32 +- 0.05) x 1E-4, where the first error in each case is statistical and the second systematic. The partial branching fractions as a function of q2 are extracted using three q2 bins. At low q2, the combined charged and neutral pion branching fractions and a Light Cone Sum Rules prescription imply |Vub| = (3.1 +- 0.2 +- 0.1 {+0.5-0.3}) x 1E-3, while using the high q2 data and two different lattice prescriptions implies |Vub| = (3.1 +- 0.3 +- 0.1 {+0.6-0.4}) x 1E-3 (HPQCD) and |Vub| = (3.3 +- 0.4 +- 0.1 {+0.6-0.4}) x 1E-3 (FNAL) respectively. In each case the errors are statistical, systematic and theoretical (associated with the prescription used). These results are obtained from a data sample that contains 657 x 1E6 BBbar pairs, collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider. All results are preliminary.