Measurement of $\omega$ meson production in pp and p$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}} = 5.02}$ TeV

TL;DR

This paper measures $$ meson production in proton-proton and proton-lead collisions at 5.02 TeV, providing new data on nuclear modification factors and meson ratios, and compares results to theoretical models.

Contribution

First measurement of $$ meson production cross sections and nuclear modification factors at LHC energies, including comparisons to event generator predictions.

Findings

$$ meson $R_{pPb}$ shows no cold nuclear matter effects within uncertainties.

The $/$ ratio decreases with increasing collision energy above 4 GeV/$c$.

Event generators show significant discrepancies in modeling $$ meson production.

Abstract

We present the measurement of the $p_{\rm T}$-differential production cross section of $\omega$ mesons in pp and p$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at midrapidity by ALICE. In addition, the first measurement of the nuclear modification factor $R_{\text{pPb}}$ for $\omega$ mesons at LHC energies is presented, complementing the existing measurements of lighter neutral mesons such as the $\pi^0$ and $\eta$. Within the measured $p_{\rm T}$-range, the $R_{\text{pPb}}$ of $\omega$ mesons is compatible with no cold nuclear matter effects within the uncertainties, consistent with previous measurements at lower energies. The $\omega/\pi^0$ ratio is presented for both collision systems, showing no collision system dependence within the uncertainties. The comparison to previously published $\omega/\pi^0$ ratios at lower and higher collision energies in pp collisions suggests a decreasing trend of the ratio above $p_{\rm T}=~4 $ GeV/$c$ with increasing collision energy. The data in both collision systems are compared to predictions from PYTHIA, EPOS LHC and DPMJET event generators, revealing significant shortcomings in these models' ability to describe the production of $\omega$ mesons.