Measurement of the nuclear modification factor of identified strange and multi-strange particles in pPb collisions at sqrt(sNN) = 5.02 TeV with CMS experiment

Measurements of strange hadron ($\mathrm{K^0_S}$, $\Lambda+\overline{\Lambda}$, $\Xi^-+\overline{\Xi}^+$, and $\Omega^-+\overline{\Omega}^+$) transverse momentum spectra in pp and pPb collisions are presented in several center-of-mass rapidity ($y_\mathrm{CM}$) intervals. The data, corresponding to integrated luminosities of approximately $40.2~\mathrm{nb}^{-1}$ and $15.6~\mu$b$^{-1}$ for pp and pPb respectively, were collected at $\sqrt{s_{_\mathrm{NN}}}=5.02~\mathrm{TeV}$ by the CMS experiment. The nuclear modification factor, $R_{\text{pPb}}$, is measured for each particle species. For $\mathrm{K^0_S}$ mesons, $R_{\text{pPb}}$ increases from $p_{\text{T}} = 0.5$ to $3.0~\mathrm{GeV}$, but is consistent with unity for $p_{\text{T}} > 3.0~\mathrm{GeV}$. In the $p_{\text{T}}$ range from 3.0 to 6.0 $\mathrm{GeV}$, $R_{\text{pPb}}$ is above unity for the three baryons with $R_{\text{pPb}}(\Omega^-+\overline{\Omega}^+) > R_{\text{pPb}}(\Xi^-+\overline{\Xi}^+) > R_{\text{pPb}}(\Lambda+\overline{\Lambda})$. In addition, the asymmetries in the $\mathrm{K^0_S}$ and $\Lambda+\overline{\Lambda}$ yields between equivalent positive and negative $y_\mathrm{CM}$ are presented as functions of $p_{\text{T}}$. The asymmetries increase away from mid-rapidity and for up to 2.0 $\mathrm{GeV}$ are found to be larger for $\mathrm{K^0_S}$ and $\Lambda+\overline{\Lambda}$ than for charged hadrons. For $p_{\text{T}} > 2.0~\mathrm{GeV}$ the asymmetries are greater for $\Lambda+\overline{\Lambda}$ than for $\mathrm{K^0_S}$. The results are compared to calculations from the ${\rm {\scriptsize \text{EPOS LHC}}}$ model with collective flow.