Production of ${\pi }^0$ and $\eta$ mesons has been measured at midrapidity in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$. Measurements were performed in ${\pi }^0\left(\eta \right)\to \gamma \gamma$ decay channel in the $1\left(2\right)-20\text{GeV}/c$ 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 $p_T=2\mathrm{GeV}/c$, 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.

• Received 4 June 2018

DOI:https://doi.org/10.1103/PhysRevC.98.054903

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Published by the American Physical Society