Measurement of the B- -> D0 l- nubar_l Branching Fraction in 62.8/fb of Belle II data

TL;DR

This paper reports a precise measurement of the B- -> D0 l- nubar_l decay branching fraction using Belle II data, confirming previous results and observing no lepton universality violation.

Contribution

First measurement of this decay mode with Belle II data, providing improved precision and testing lepton universality in B meson decays.

Findings

Branching fraction measured as (2.29 +/- 0.05(stat) +/- 0.08(syst))%.

Electron to muon branching ratio found to be 1.04 +/- 0.05(stat) +/- 0.03(syst).

Results are consistent with the Standard Model expectations.

Abstract

We report a measurement of the branching fraction of the semileptonic decay B- -> D0 l- nubar_l (and its charge conjugate) using 62.8/fb of Upsilon(4S) -> B Bbar data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy e+ e- collider. The neutral charm meson is searched for in the decay mode D0 -> K- pi+ and combined with a properly charged identified lepton (electron or muon) to reconstruct this decay. No reconstruction of the second B meson in the Upsilon(4S) event is performed. We obtain Br( B- -> D0 l- nubar_l ) = (2.29 +/- 0.05(stat) +/- 0.08(syst))%, in agreement with the world average of this decay. We also determine the ratio of the electron to muon branching fractions to be R(e/mu) = 1.04 +/- 0.05(stat) +/- 0.03(syst) and observe no deviation from lepton universality.