Multi-strange baryon production in p-Pb collisions at √s_NN = 5.02 TeV

The multi-strange baryon yields in PbPb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, Ξ and Ω production rates have been measured with the ALICE experiment as a function of transverse momentum, p_T, in p-Pb collisions at a centre-of-mass energy of √s_NN = 5.02  TeV. The results cover the kinematic ranges 0.6 GeV/c < p_T < 7.2 GeV/c and 0.8 GeV/c < p_T < 5 GeV/c , for Ξ and Ω respectively, in the common rapidity interval − 0.5 < y_CMS < 0 . Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The p_T spectra are analysed as a function of event charged-particle multiplicity, which in pPb collisions ranges over one order of magnitude and lies between those observed in pp and Pb-Pb collisions. The measured p_T distributions are compared to the expectations from a Blast-Wave model. The parameters which describe the production of lighter hadron species also describe the hyperon spectra in high multiplicity p-Pb collisions. The yield of hyperons relative to charged pions is studied and compared with results from pp and Pb-Pb collisions. A continuous increase in the yield ratios as a function of multiplicity is observed in p-Pb data, the values of which range from those measured in minimum bias pp to the ones in Pb-Pb collisions. A statistical model qualitatively describes this multiplicity dependence using a canonical suppression mechanism, in which the small volume causes a relative reduction of hadron production dependent on the strangeness content of the hyperon.