Unified description of transverse momentum spectrums contributed by soft and hard processes in high-energy nuclear collisions

Abstract

The transverse momentum spectrums of π −, π +, K −, K +, $$\bar p$$ , and p produced in p-Pb collisions at √s NN = 502 TeV measured by the CMS Collaboration and in Pb-Pb collisions at √s NN = 2.76 TeV measured by the ALICE Collaboration are described by a two-component Erlang distribution. The first component corresponds to “soft” excitation process and contributes in the low transverse momentum region, which is contributed by 2–5 partons (sea quarks and gluons) with strong interactions. The second component corresponds to “hard” scattering process and contributes in the high transverse momentum region, which is contributed by 2 partons (valent quarks) with violent head-on collision. Each parton source contributes an exponential transverse momentum spectrum. Both the soft and hard processes result in an Erlang distribution. The transverse momentum spectrums of final-state charged particles are then described by the two-component Erlang distribution. The contribution ratio (30–40%) of the hard process extracted from nuclear collisions at the Large Hadron Collider is consistent with that (17–46%) obtained from other methods.