Strangeness production as a function of charged particle multiplicity in proton–proton collisions

Abstract

Recent measurements performed in high-multiplicity proton-proton (pp) and proton-lead (p-Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb-Pb) collisions. These observations warrant a comprehensive measurement of the production of identified particles. We report on the production of K 0 S , Λ, Λ, Ξ ± and Ω ± at mid-rapidity measured as a function of multiplicity in pp collisions at √ s = 7 TeV with the ALICE experiment. Spectral shapes studied both for individual particles and via particle ratios such as (Λ/K 0 S ) as a function of p T exhibit an evolution with event multiplicity and the production rates of hyperons are observed to increase more strongly than those of non-strange hadrons. These phenomena are qualitatively similar to the ones observed in p-Pb and Pb-Pb collisions.

Thermodynamical string fragmentation

“…That is, π ± obtains a too large p ⊥ in Pythia and baryons a too small one. Recently p ⊥ has also been presented as a function of n ch , inclusive [47] and for different hadron species [48], providing a more differential information on this mismatch. In figure 1 we show these observables and compare default Pythia with data, with the above expected conclusions.…”

“…Specifically, a distribution more sharply peaked at b = 0 gives a longer tail towards high multiplicities. [46,48] and ATLAS [47] data. The data in the bottom plots is taken to be an estimate of the logarithmic fits in [48] and therefore no error bars are included.…”

“…[47], CMS [52,83] and ALICE data [51]. [46,48] and ATLAS [47] data. The data in the bottom plots is taken to be an estimate of the logarithmic fits in [48] and therefore no error bars are included.…”

“…[46,48] and ATLAS [47] data. The data in the bottom plots is taken to be an estimate of the logarithmic fits in [48] and therefore no error bars are included. Figure 16: Ratio of yields with respect to (π + + π − ) as a function of the charged multiplicity.…”

Multiplicity-dependent pT distributions of identified particles in pp collisions at 7 TeV within the HIJING/ BB¯Pop1, Petrovici2 2018Phys. Rev. C1000View full textAdd to dashboardCite

“…The charged-particle densities dN ch /dη are integrated values at mid-pseudorapidity |η| < 0.5 for that class of events. The p T distributions of ID particles were recently measured in pp collisions at √ s = 7 TeV for different multiplicity classes of events by the ALICE Collaboration [68][69][70][71].…”