Central exclusive production at LHCb

TL;DR

This paper reports on LHCb measurements of central exclusive production of various mesons and meson pairs in proton-proton collisions at different energies, providing insights into gluon distributions at very low Bjorken-x values.

Contribution

First measurements of central exclusive production of mesons and meson pairs at LHCb across multiple energies, utilizing new detector components to improve background suppression.

Findings

Measured production cross sections at 7, 8, and 13 TeV.

Extended sensitivity to gluon distributions down to x=2×10^{-6}.

Compared results with other experiments and theoretical models.

Abstract

The LHCb collaboration has measured central exclusive production of $J/\psi$, $\psi(2S)$, and $\Upsilon$ mesons as well as $J/\psi J/\psi$, $J/\psi\psi(2S)$, $\psi(2S)\psi(2S)$, and $\chi_c\chi_c$ meson pairs in proton-proton collisions. The analyses of $\Upsilon$ and charmonium pairs are performed at the centre-of-mass energies of 7 TeV and 8 TeV, and those of $J/\psi$ and $\psi(2S)$ are done at 7 TeV and 13 TeV. The analysis at 13 TeV involves the use of new shower counters. These allow a reduction in the background by vetoing events with activity in an extended region in rapidity. The measurements of central exclusive production at LHCb are sensitive to gluon distributions for Bjorken-$x$ values down to $2\times10^{-6}$ (at 13 TeV). An overview of the LHCb results is presented and compared to existing measurements of other experiments and theoretical calculations.