Measurement of the decay $B^0\to\pi^-\ell^+\nu$ and determination of $|V_{ub}|$

TL;DR

This paper reports a precise measurement of the decay rate of $B^0 o ext{pi}^- ext{l}^+ u$ and determines the CKM matrix element $|V_{ub}|$ using a large data sample and lattice QCD inputs, improving our understanding of quark flavor transitions.

Contribution

It provides the most accurate measurement to date of the branching fraction and $|V_{ub}|$ for this decay, combining experimental data with lattice QCD results for model-independent analysis.

Findings

Branching fraction $ imes 10^{-4}$: 1.49 ± 0.04 (stat) ± 0.07 (syst)

$|V_{ub}|$ value: (3.43 ± 0.33)×10^{-3}

Large data sample of 657 million $Bar{B}$ events

Abstract

We present a measurement of the charmless semileptonic decay $B^0\to\pi^-\ell^+\nu$ using a data sample containing 657$\times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider operating near the $\Upsilon(4S)$ resonance. We determine the total branching fraction of the decay, $\mathcal{B}(B^0\to\pi^-\ell^+\nu)=(1.49\pm 0.04{(\mathrm{stat})}\pm 0.07{(\mathrm{syst})})\times 10^{-4}$. We also report a new precise measurement of the differential decay rate, and extract the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ using model-independent and -dependent approaches. From a simultaneous fit to the measured differential decay rate and lattice QCD results, we obtain $|V_{ub}|=(3.43\pm 0.33)\times 10^{-3}$, where the error includes both statistical and systematic uncertainties.