# Production of ${\pi }^{0}$ and $\eta$ mesons in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{NN}}}=200\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$

19 November 2018

Abstract: Production of ${\pi }^{0}$ and $\eta$ mesons has been measured at midrapidity in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{NN}}}=200\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$. Measurements were performed in ${\pi }^{0}\left(\eta \right)\to \gamma \gamma$ decay channel in the $1\left(2\right)-20\phantom{\rule{0.28em}{0ex}}\text{GeV}/c$ transverse momentum range. A strong suppression is observed for ${\pi }^{0}$ and $\eta$ meson production at high transverse momentum in central $\mathrm{Cu}+\mathrm{Au}$ collisions relative to the $p+p$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to $\mathrm{Au}+\mathrm{Au}$ with comparable nuclear overlap. The $\eta /{\pi }^{0}$ ratio measured as a function of transverse momentum is consistent with ${m}_{T}$-scaling parametrization down to ${p}_{T}=2\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}/c$, its asymptotic value is constant and consistent with $\mathrm{Au}+\mathrm{Au}$ 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 $\mathrm{Cu}+\mathrm{Cu}$ collisions either does not affect the jet fragmentation into light mesons or it affects the ${\pi }^{0}$ and $\eta$ the same way.

Published in: Physical Review C 98 (2018)