the nuclear overlap function () in various centrality intervals are estimated with a Glauber-model Monte-Carlo simulation [@Miller:2007ri] folded with the BBC response. The average values of and for different centrality classes of collisions are listed in Table \[tab0\].

The measurements are based on two data sets. Up to moderate ($<8$) $6.9\times10^{9}$ MB events satisfying a vertex cut of $|z_{\rm BBC}|< 20$ cm are used. To improve statistics and extend the range to higher an additional sample was collected with one of the EMCal hardware triggers (ERT-A). This trigger required the presence of at least one high-energy shower in the EMCal. After offline calibration it was found that the ERT-A trigger reached full efficiency for photons with energy above 4.5–5GeV depending on location in the calorimeter. The accumulated ERT-A data sample after the same $|z_{\rm BBC}|<20$cm vertex cut corresponds to $1.8\times10^{10}$ sampled MB events, which is a factor of three more than the MB sample. MB data is used to measure meson yields at $p_T<8$ GeV/$c$, and ERT-A data set is used at higher momenta.

Reconstruction of $\pi^0$ and $\eta$ mesons is performed via their decay modes $\pi^0\rightarrow\gamma\gamma$ and $\eta\rightarrow\gamma\gamma$. Photons are measured in the EMCal [@Aphecetche:2003zr] located in the two 