Study of $\chi_{b}$ meson production in pp collisions at $\sqrt{s}=7$ and 8TeV and observation of the decay $\chi_{b}\rightarrow \Upsilon(3S) \gamma$

TL;DR

This paper reports on the production of $$ mesons in proton-proton collisions at 7 and 8 TeV, measuring decay fractions, and first observing the $(3P) S$ transition with a new mass measurement.

Contribution

It provides the first observation of the $(3P) S$ radiative decay and measures the $(3P)$ mass in proton-proton collisions at LHCb.

Findings

First observation of $(3P) S$ decay

Mass of $(3P)$ measured as 10511.3 MeV/c^2

Fraction of $$ from $$ decays as a function of $$ transverse momentum

Abstract

A study of $\chi_{b}$ meson production at LHCb is performed on proton-proton collision data, corresponding to 3.0fb$^{-1}$ of integrated luminosity collected at centre-of-mass energies $\sqrt{s}=7$ and 8TeV. The fraction of $\Upsilon(nS)$ mesons originating from $\chi_{b}$ decays is measured as a function of the $\Upsilon$ transverse momentum in the rapidity range $2.0 < y^{\Upsilon} < 4.5$. The radiative transition of the $\chi_{b}(3P)$ meson to $\Upsilon(3S)$ is observed for the first time. The $\chi_{b1}(3P)$ mass is determined to be $$m(\chi_{b1}(3P)) = 10\,511.3 \pm 1.7 \pm 2.5 MeV/c^2,$$ where the first uncertainty is statistical and the second is systematic.