Abstract
The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity (left| yright| < 0.5) are measured in proton-proton collisions at sqrt{s} = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of mathrm{K}^{0}_{S}, Lambda , Xi , and Omega increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV.
Highlights
An enhanced production of strange hadrons in heavy-ion collisions was suggested as a signature for the creation of a Quark-Gluon Plasma (QGP) [7,8]
In central heavy-ion collisions, the yields of strange hadrons turn out to be consistent with the expectation from a grandcanonical ensemble, i.e. the production of strange hadrons is compatible with thermal equilibrium, characterised by a common temperature
We present the measurement of the yields and transverse momentum distributions of single-strange (K0S, ) and multi-strange ( −, +, −, +) particles at mid-rapidity, |y| < 0.5, with the ALICE detector [24]
Summary
An enhanced production of strange hadrons in heavy-ion collisions was suggested as a signature for the creation of a Quark-Gluon Plasma (QGP) [7,8]. In the case of p-Pb collisions, the yields of strange hadrons relative to pions reach values close to those observed in Pb–Pb collisions at full equilibrium. These are surprising observations, because thermal strangeness production was considered to be a defining feature of heavy-ion collisions, and because none of the commonly-used pp Monte Carlo models reproduced the existing data [3,21].
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