Abstract
Two-particle Azimuthal correlations are measured with the ALICE apparatus in pp collisions at sqrt{s} = 13 TeV to explore strangeness- and multiplicity-related effects in the fragmentation of jets and the transition regime between bulk and hard production, probed with the condition that a strange meson (mathrm {K_S}^{0}) or baryon (Lambda ) with transverse momentum p_{mathrm T} >3 GeV/c is produced. Azimuthal correlations between kaons or Lambda hyperons with other hadrons are presented at midrapidity for a broad range of the trigger (3< p_mathrm {T}^mathrm {trigg} < 20 GeV/c) and associated particle p_{mathrm T} (1 GeV/c< p_mathrm {T}^mathrm {assoc} < p_mathrm {T}^mathrm {trigg} ), for minimum-bias events and as a function of the event multiplicity. The near- and away-side peak yields are compared for the case of either mathrm {K_S}^{0} or Lambda ({overline{Lambda }}) being the trigger particle with that of inclusive hadrons (a sample dominated by pions). In addition, the measurements are compared with predictions from PYTHIA 8 and EPOS LHC event generators.
Highlights
Particle production as a function of the event charged-particle multiplicity in proton–proton collisions at the LHC has revealed interesting patterns
The pairs of identified daughter tracks are combined to V0 candidates, which are accepted if their invariant mass is within 3σ (1σ for KS0 is in the range 0.0039–0.0075 GeV/c2 and for in 0.0021– 0.0033 GeV/c2 depending on pT) from the nominal value
Included are the correlation functions predicted by Monte Carlo (MC) event generators widely used by the LHC collaborations: PYTHIA8 with the standard Monash tune, which includes colour re-connection as final-state effects [13], PYTHIA8 Monash tune with shoving [14] and EPOS LHC [12]
Summary
Particle production as a function of the event charged-particle multiplicity in proton–proton (pp) collisions at the LHC has revealed interesting patterns. It was recently shown that in pp collisions the near-side long-range (in pseudorapidity) ridge yield (of bulk particles) in high-multiplicity events remains present for events which are biased, through either a Z boson [17], a leading high- pT particle or a jet [18] These findings are interesting per se and motivate the quest to find or exclude jet quenching in high-multiplicity events in small collision systems, with differences in the observed effects on gluon, light and heavy quark jets. Hcoylpleisrioonnsswatit√h osth=er1h3adTroeVns are for studied a broad at midrapidity in pp range of the trigger (3 < pTtrigg < 20 GeV/c) and associated particle pT (1 GeV/c < pTassoc < pTtrigg), for minimum bias events and as a function of the event multiplicity measured at forward rapidities Such correlations encode effects of fragmentation, hadronisation and parton showering as well as possible collectivity and jet quenching.
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