Measurement of Exclusive B -> X_ulnu Decays with D^(*)lnu Decay Tagging

TL;DR

This paper measures the branching fractions of charmless semileptonic B decays using D^(*)lnu decay tagging, providing insights into V_{ub} with high purity but limited statistics, based on 140 fb^{-1} data from the Belle detector.

Contribution

It introduces a method to measure B->X_u l nu decays with high purity using D^(*)lnu tagging, offering new experimental results for branching fractions and V_{ub} extraction.

Findings

Branching fraction for B0->pi^-l^+nu: (1.76 ± 0.28 ± 0.20 ± 0.03)×10^{-4}

Branching fraction for B0->rho^-l^+nu: (2.54 ± 0.78 ± 0.85 ± 0.30)×10^{-4}

Results are preliminary and include q^2 interval measurements.

Abstract

We report on a measurement of the charmless semileptonic B decays, B0->pi^-l^+nu and B0->rho^-l^+nu, based on 140 fb^{-1} data collected with the Belle detector at the KEKB e^+e^- asymmetric collider. In this analysis, accompanying B mesons are reconstructed from semileptonic B->D^(*)lnu decays, which enables us to detect the signal with high purity and with marginal statistics. We found branching fractions of Br(B0->pi^-l^+nu)=(1.76 \pm 0.28 \pm 0.20 \pm 0.03)10^{-4} and Br(B0->rho^-l^+nu)=(2.54 \pm 0.78 \pm 0.85 \pm 0.30)10^{-4}, where the errors are statistical, experimental systematic, systematic due to form-factor uncertainties. We present also the branching fractions in three q^2 intervals; q^2 < 8, 8 \leq q^2 < 16, q^2 \geq 16 GeV^2/c^2, for each decay mode. Based on these results, the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V_{ub} is extracted. All of the presented results are preliminary.