Production of $\pi^0$ and $\eta$ mesons in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV

TL;DR

This study measures neutral meson production in Cu+Au collisions at 200 GeV, revealing significant suppression at high transverse momentum in central collisions, with results consistent across different collision systems and energies, indicating similar jet fragmentation behavior.

Contribution

First measurement of $$ and $$ meson production in Cu+Au collisions at 200 GeV, showing suppression patterns and $/$ ratios consistent with other systems and models.

Findings

Strong suppression of mesons at high $p_T$ in central collisions.

$/$ ratio is constant and matches $m_T$-scaling.

Results are consistent with other collision systems and energies.

Abstract

Production of $\pi^0$ and $\eta$ mesons has been measured at midrapidity in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV. Measurements were performed in $\pi^0(\eta)\rightarrow\gamma\gamma$ decay channel in the 1(2)-20 GeV/$c$ transverse momentum range. A strong suppression is observed for $\pi^0$ and $\eta$ meson production at high transverse momentum in central Cu$+$Au collisions relative to the $p$$+$$p$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au$+$Au with comparable nuclear overlap. The $\eta/\pi^0$ ratio measured as a function of transverse momentum is consistent with $m_T$-scaling parameterization down to $p_T=$2 GeV/$c$, its asymptotic value is constant and consistent with Au$+$Au and $p$$+$$p$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $e^+e^-$ collisions in a range of collision energies $\sqrt{s_{_{NN}}}=$3--1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu$+$Cu collisions either does not affect the jet fragmentation into light mesons or it affects the $\pi^0$ and $\eta$ the same way.