System size and energy dependence of the mean transverse momentum fluctuations at the LHC

Abstract

Event-by-event fluctuations of the event-wise mean transverse momentum, $⟨p_{\mathrm{T}}⟩$, of charged particles produced in proton$-$proton (pp) collisions at $\sqrt{s}$ = 5.02 TeV, Xe$-$Xe collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.44 TeV, and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.0 TeV are studied using the ALICE detector based on the integral correlator $⟨⟨\Delta p_{\mathrm{T}}\Delta p_{\mathrm{T}}⟩⟩$. The correlator strength is found to decrease monotonically with increasing produced charged-particle multiplicity measured at midrapidity in all three systems. In Xe$-$Xe and Pb$-$Pb collisions, the multiplicity dependence of the correlator deviates significantly from a simple power-law scaling as well as from the predictions of the HIJING and AMPT models. The observed deviation from power-law scaling is expected from transverse radial flow in semicentral to central Xe$-$Xe and Pb$-$Pb collisions. In pp collisions, the correlation strength is also studied by classifying the events based on the transverse spherocity, $S_0$, of the particle production at midrapidity, used as a proxy for the presence of a pronounced back-to-back jet topology. Low-spherocity (jetty) events feature a larger correlation strength than those with high spherocity (isotropic). The strength and multiplicity dependence of jetty and isotropic events are well reproduced by calculations with the PYTHIA 8 and EPOS LHC models.

28 pages, 8 captioned figures, 1 table, authors from page 22, figures at http://alice-publications.web.cern.ch/node/11736

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Cited by in corpus (2)

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