First observation of the decay $B_{s2}^*(5840)^0 \to B^{*+} K^-$ and studies of excited $B_s$ mesons

TL;DR

This paper reports the first observation of a specific decay mode of the $B_{s2}^*(5840)^0$ meson, measures its properties with high precision, and provides insights into the excited $B_s$ meson states using LHCb data.

Contribution

The study presents the first observation of the decay $B_{s2}^*(5840)^0 o B^{*+} K^-$ and measures the widths and masses of excited $B_s$ mesons with unprecedented accuracy.

Findings

First observation of $B_{s2}^*(5840)^0 o B^{*+} K^-$ decay

Precise measurements of meson masses and widths

Mass difference $m(B^{*+})-m(B^+)$ measured accurately

Abstract

Properties of the orbitally excited (L=1) $B_s$ states are studied using 1.0 fb$^{-1}$ of pp collisions at $\sqrt{s} =7$ TeV collected with the LHCb detector. The first observation of the $B_{s2}^*(5840)^0$ meson decaying to $B^{*+} K^-$ is reported, and the corresponding branching fraction measured relative to the $B^+ K^-$ decay mode. The $B_{s1}(5830)^0 \to B^{*+} K^-$ decay is observed as well. The width of the $B_{s2}^*(5840)^0$ state is measured for the first time and the masses of the two states are determined with the highest precision to date. The observation of the $B_{s2}^*(5840)^0 \to B^{*+} K^-$ decay favours the spin-parity assignment $J^P = 2^+$ for the $B_{s2}^*(5840)^0$ meson. In addition, the most precise measurement of the mass difference $m(B^{*+})-m(B^+) = 45.01 \pm 0.30 (stat) \pm 0.23 (syst)$ MeV/$c^2$ is obtained.