Measurement of Differential Branching Fractions of Inclusive ${B \to X_u \, \ell^+\, \nu_{\ell}}$ Decays

TL;DR

This paper reports the first measurements of differential branching fractions for inclusive B to X_u l+ nu decays, using the full Belle dataset, providing detailed distributions as functions of various kinematic variables.

Contribution

It presents the first experimental determination of differential branching fractions for inclusive B to X_u l+ nu decays, using a comprehensive dataset and advanced background subtraction techniques.

Findings

Differential branching fractions as functions of multiple kinematic variables.

Comparison of measured distributions with theoretical predictions.

First such measurements using the full Belle dataset.

Abstract

The first measurements of differential branching fractions of inclusive semileptonic ${B \to X_u \, \ell^+\, \nu_{\ell}}$ decays are performed using the full Belle data set of 711 fb$^{-1}$ of integrated luminosity at the $\Upsilon(4S)$ resonance and for $\ell = e, \mu$. Differential branching fractions are reported as a function of the lepton momentum, the four-momentum-transfer squared, light-cone momenta, the hadronic mass, and the hadronic mass squared. They are obtained by subtracting the backgrounds from semileptonic ${B \to X_c \, \ell^+\, \nu_{\ell}}$ decays and other processes, and corrected for resolution and acceptance effects. The measured distributions are compared to predictions from inclusive and hybrid ${B \to X_u \, \ell^+\, \nu_{\ell}}$ calculations.