Measurement of the relative $B^{-} \!\rightarrow D^{0} / D^{*0} / D^{**0} \mu^{-} \overline{\nu}_\mu$ branching fractions using $B^{-}$ mesons from $\overline{B}{}_{s2}^{*0}$ decays

TL;DR

This paper measures the relative branching fractions of $B^-$ meson decays into different charmed states using a novel technique that reconstructs the $B^-$ momentum via $ar{B}_{s2}^{*0}$ decays, providing new insights into semileptonic decay composition.

Contribution

The study introduces a first-time application of a method to distinguish $D^0$, $D^{*0}$, and $D^{**0}$ contributions in $B^-$ decays using the $ar{B}_{s2}^{*0}$ decay channel for momentum reconstruction.

Findings

Measured $D^0$ contribution as 25%

Measured $D^{**0}$ contribution as 21%

Determined the remaining $D^{*0}$ contribution

Abstract

The decay of the narrow resonance $\overline{B}{}_{s2}^{*0}\!\rightarrow B^- K^+$ can be used to determine the $B^-$ momentum in partially reconstructed decays without any assumptions on the decay products of the $B^-$ meson. This technique is employed for the first time to distinguish contributions from $D^0$, $D^{*0}$, and higher-mass charmed states ($D^{**0}$) in semileptonic $B^-$ decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb${}^{-1}$ collected with the LHCb detector in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The resulting branching fractions relative to the inclusive $B^- \!\rightarrow D^0 X \mu^- \overline{\nu}_\mu$ are $f_{D^0} = \mathcal{B}( B^- \rightarrow D^0\mu^-\overline{\nu}_\mu )/\mathcal{B}( B^- \rightarrow D^0 X \mu^- \overline{\nu}_\mu ) = 0.25 \pm 0.06$, $f_{D^{**0}} = \mathcal{B}( B^- \rightarrow ( D^{**0} \rightarrow D^0 X)\mu^-\overline{\nu}_\mu )/\mathcal{B}( B^- \rightarrow D^0 X \mu^- \overline{\nu}_\mu ) = 0.21 \pm 0.07$, with $f_{D^{*0}} = 1 - f_{D^0} - f_{D^{**0}}$ making up the remainder.