Measurement of the $B^0_s\rightarrow J/\psi K^{*0}$ branching fraction and angular amplitudes

TL;DR

This paper reports the measurement of the branching fraction and angular amplitudes of the decay $B^0_s ightarrow J/ heta K^{*0}$ using LHCb data, providing insights into decay dynamics and polarization states.

Contribution

First measurement of the $B^0_s ightarrow J/ heta K^{*0}$ branching fraction and polarization fractions with LHCb data, including angular analysis and systematic uncertainties.

Findings

Branching fraction of $(4.4_{-0.4}^{+0.5} ext{(stat)} ext{ and systematic uncertainties}) imes 10^{-5}$.

Polarization fractions: $f_L = 0.50 \

f_{||} = 0.19^{+0.10}_{-0.08}$.

Abstract

A search for the decay $B^0_s\rightarrow J/\psi K^{*0}$ with $K^{*0} \rightarrow K^-\pi^+$ is performed with 0.37 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 7 TeV collected by the LHCb experiment, finding a $\Bs \to J\psi K^-\pi^+$ peak of $114 \pm 11$ signal events. The $K^-\pi^+$ mass spectrum of the candidates in the $B^0_s$ peak is dominated by the $K^{*0}$ contribution. Subtracting the non-resonant $K^-\pi^+$ component, the branching fraction of \BsJpsiKst is $(4.4_{-0.4}^{+0.5} \pm 0.8) \times 10^{-5}$, where the first uncertainty is statistical and the second systematic. A fit to the angular distribution of the decay products yields the \Kst polarization fractions $f_L = 0.50 \pm 0.08 \pm 0.02$ and $f_{||} = 0.19^{+0.10}_{-0.08} \pm 0.02$.