Multiplicity dependence of (multi-)strange hadron production in proton-proton collisions at $$\sqrt{s}$$ = 13 TeV

Abstract

The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity (|y| < 0.5) are measured in proton-proton collisions at √ s = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of K 0 S , , , and 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.

(Anti-)deuteron production in pp collisions at $$\sqrt{s}=13 \ \text {TeV}$$

“…The particle identification is based on the difference between the measured time-offlight and its expected value, computed for each mass hypoth- Table 1 Summary of the relevant information about the multiplicity classes and the fits to the measured transverse momentum spectra of anti-deuterons. dN ch /dη is the mean pseudorapidity density of the primary charged particles [25]. n and C are the parameters of the Lévy-Tsallis fit function [27].…”

“…However, in this analysis classes IV and V are merged into a single class to achieve a better statistical precision. The multiplicity classes are determined from the sum of the V0 signal amplitudes and defined in terms of percentiles of the INEL> 0 pp cross section, where INEL > 0 events are defined as collisions with at least one charged particle in the pseudorapidity region |η| <1 [25]. The mean charged particle multiplicity dN ch /dη for each class is reported in Table 1.…”

“…All the selected events are required to have at least one charged particle in the acceptance, i.e. in the pseudo-rapidity region |η| < 1 (INEL > 0) [25]. Due to the imperfection of the trigger, some INEL > 0 events are wrongly rejected (event loss).…”

Particle production and flow-like effects in small systems

“…The ALICE Collaboration has performed the strangeness analysis using pp data at √ s = 13 TeV [23], and compared data with MC event generators predictions. PYTHIA 8.210 [24] (tune Monash [25]) gives a reasonable description of the K 0…”

Measurement of fs/fu Variation with Proton-Proton Collision Energy and B

“…[14] is not used due to disputed theoretical uncertainties arising from factorization assumption.) In the different context of light and strange hadrons, the ALICE experiment has observed a dependence of their production ratios on the multiplicity of the event [15][16][17]. In this analysis, this dependence is not studied, owing to technical reasons; however, such behavior will be the subject of future studies.…”