Observation of muonic Dalitz decays of $\chi_{b}$ mesons and precise spectroscopy of hidden-beauty states

TL;DR

This paper reports the observation of muonic Dalitz decays of $ ext{b}$-quarkonium states and uses these decays for precise spectroscopy of hidden-beauty mesons, enhancing understanding of their mass structure.

Contribution

It presents the first observation of specific muonic Dalitz decays of $ ext{b}$-quarkonium states and employs these decays for high-precision measurements of hidden-beauty meson masses.

Findings

Observation of $ ext{b}$-quarkonium muonic Dalitz decays with high significance

Precise measurements of mass splittings of hidden-beauty states

Enhanced understanding of bottomonium spectroscopy

Abstract

The decays of the $\chi_{b1}(1P)$, $\chi_{b2}(1P)$, $\chi_{b1}(2P)$ and $\chi_{b2}(2P)$ mesons into the $\Upsilon(1S)\mu^+\mu^-$ final state are observed with a high significance using proton-proton collision data collected with the LHCb detector and corresponding to an integrated luminosity of 9fb$^{-1}$. The newly observed decays together with the $\Upsilon(2S)\rightarrow \Upsilon(1S)\pi^+\pi^-$ and $\Upsilon(3S)\rightarrow \Upsilon(2S)\pi^+\pi^-$ decay modes are used for precision measurements of the mass and mass splittings for the hidden-beauty states.