Nuclear modification factors of strange and multi-strange particles in pPb collisions with the CMS experiment

Recent observation of collective effects in high-multiplicity pp and pA collisions raise the question of whether QGP can also be formed in the smaller systems. Systematic studies of the strange particle abundance and nuclear modification factors can shed light on this issue. The CMS experiment has excellent strange-particle reconstruction capabilities overa broad kinematic range in pp and pPb collisions. The spectra of $K_{s}^{0}, \Lambda +\bar{\Lambda}, \Xi^- + \Xi^+$, and $\Omega^- + \bar{\Omega}^+$ hadrons have been measured in various rapidity regions as a function of p Tin pp and pPb collisions at 5.02 TeV. Based on the measurements of these spectra, nuclear modification factors of $K_{s}^{0}, \Lambda +\bar{\Lambda}, \Xi^- + \Xi^+$, and $\Omega^- + \bar{\Omega}^+$ in mid-rapidity are measured. Since pPb is an asymmetric system, the nuclear modification factor of $K_{s}^{0}, \Lambda +\bar{\Lambda}, \Xi^- + \Xi^+$, and $\Omega^- + \bar{\Omega}^+$ in Pb-going direction are compared to those in p-going direction. These final results for nuclearmodification factors measured out to high-pTcan be helpful in discussing the implications ofcollective behavior and energy loss. In addition, the measurement of the forward-backward rapidity yield asymmetries of $K_{s}^{0}$ and $\Lambda$ as a function of pT provide sensitivity to initial state effects, such as shadowing in the nuclear parton distributions.