Coherent $\rho^0$ photoproduction in ultra-peripheral Pb-Pb collisions at $\mathbf{\sqrt{\textit{s}_{\rm NN}}} = 2.76$ TeV

TL;DR

This paper presents the first measurement of coherent $ ho^0$ meson photoproduction in ultra-peripheral Pb-Pb collisions at the LHC, providing new data on meson production cross sections and nuclear breakup effects.

Contribution

It reports the first LHC measurement of coherent $ ho^0$ production in ultra-peripheral Pb-Pb collisions, including cross sections and breakup scenario analysis.

Findings

Measured cross section: 425 ± 10 (stat.) +42/-50 (sys.) mb

Compared results with lower energy data and models

Analyzed nuclear breakup scenarios and yields

Abstract

We report the first measurement at the LHC of coherent photoproduction of $\rho^0$ mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for $\rho^0$ production are studied in the $\pi^+ \pi^-$ decay channel at mid-rapidity. The production cross section in the rapidity range $|y|<0.5$ is found to be $\mathrm{d}\sigma/\mathrm{d}y = 425 \pm 10 \, (\mathrm{stat.})$ $^{+42}_{-50} \, (\mathrm{sys.})$ mb. Coherent $\rho^0$ production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions.