Transverse momentum, rapidity, and centrality dependence of Charged Particle Production in $p$+Pb $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV collisions measured by ATLAS experiment at the LHC

ATLAS has measured transverse momentum ($p_{\mathrm{T}}$) and pseudorapidity ($\eta$) distributions of charged particles produced in $\sqrt{s_{\mathrm{NN}}}=5.02$ GeV $p$+Pb collisions. Charged particles were measured over $|\eta|<2.5$ and $0.1<p_{T}<22$ GeV in a data set corresponding to an integrated luminosity of 1~$\mu {\rm b}^{-1}$. The $p$+Pb collision centrality was characterized by the total transverse energy measured in one of the ATLAS forward calorimeters. Charged particle rapidity distributions were obtained by assuming a pion mass for all charged particles and correcting for the contributions of kaons and protons. The $p$+Pb charged particle per-event yields were compared to charged particle cross-sections in $p+p$ collisions obtained by interpolating measurements at $\sqrt{s} = 2.76$ TeV and 7 TeV also presented in this note to 5.02 TeV. Results are presented in the form of charged particle nuclear modification factors, $R_{p+\mathrm{Pb}}$, and the central to peripheral ratios, $R_{\mathrm{CP}}$. The $R_{p+\mathrm{Pb}}$ and $R_{\mathrm{CP}}$ values are found to vary significantly as a function of rapidity and transverse momentum. A broad peak is observed for all centralities and rapidities in $R_{p+\mathrm{Pb}}(p_{\mathrm{T}})$ and $R_{\mathrm{CP}}(p_{\mathrm{T}})$ in the vicinity of $p_{\mathrm{T}} \sim 3$ GeV. However, that peak is highest in most central collisions and for rapidities in the lead-going direction.