Multi-strange baryon production in p-Pb collisions at \(\sqrt{s_\mathbf{NN}}=5.02\) TeV

Abstract

The multi-strange baryon yields in Pb--Pb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, \(\Xi\) and \(\Omega\) production rates have been measured with the ALICE experiment as a function of transverse momentum, \({p_{\rm T}}\), in p-Pb collisions at a centre-of-mass energy of \({\sqrt{s_{\rm NN}}}\) = 5.02 TeV. The results cover the kinematic ranges 0.6 GeV/\(c<{p_{\rm T}} <\)7.2 GeV/\(c\) and 0.8 GeV/\(c<{p_{\rm T}}<\) 5 GeV/\(c\), for \(\Xi\) and \(\Omega\) respectively, in the common rapidity interval -0.5 \(<{y_{\rm CMS}}<\) 0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The \({p_{\rm T}}\) spectra are analysed as a function of event charged-particle multiplicity, which in p-Pb collisions ranges over one order of magnitude and lies between those observed in pp and Pb-Pb collisions. The measured \({p_{\rm T}}\) 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. The yield of hyperons relative to charged pions is studied and compared with results from pp and Pb-Pb collisions. A statistical model is employed, which describes the change in the ratios with volume using a canonical suppression mechanism, in which the small volume causes a species-dependent relative reduction of hadron production. The calculations, in which the magnitude of the effect depends on the strangeness content, show good qualitative agreement with the data.