Transverse momentum spectra in high-energy nucleus-nucleus, proton-nucleus and proton-proton collisions

The transverse momentum distributions of final-state particles produced in nucleus-nucleus （AA）, proton-nucleus （pA）, and proton-proton （pp） collisions at high energies are investigated using a multisource ideal gas model. Our calculated results show that the contribution of hard emission can be neglected in the study of transverse momentum spectra of charged pions and kaons produced in Cu-Cu collisions at √SNN=22.5 GeV. And if we consider the contribution of hard emission, the transverse momentum spectra of p and ^-p produced in Cu-Cu collisions at √SNN=22.5 GeV, K^0 produced in Pb-Pb collisions at 158 A GeV, J/φ particles produced in p-Pb collisions at 400 GeV and π^＋, K^＋, p produced in proton-proton collisions at √s=200 GeV, can be described by the model, especially in the tail part of spectra.

Effective(kinetic freeze-out) temperature, transverse flow velocity, and kinetic freeze-out volume in high energy collisions

The transverse momentum spectra of different types of particles produced in central and peripheral gold–gold(Au–Au)and inelastic proton–proton(pp)collisions at the Relativistic Heavy Ion Collider,as well as in central and peripheral lead-lead(Pb–Pb)and pp collisions at the Large Hadron Collider,are analyzed by the multi-component standard(Boltzmann–Gibbs,Fermi–Dirac,and Bose–Einstein)distributions.The obtained results from the standard distribution give an approximate agreement with the measured experimental data by the STAR,PHENIX,and ALICE Collaborations.The behavior of the effective(kinetic freeze-out)temperature,transverse flow velocity,and kinetic freeze-out volume for particles with different masses is obtained,which observes the early kinetic freezeout of heavier particles as compared to the lighter particles.The parameters of emissions of different particles are observed to be different,which reveals a direct signature of the mass-dependent differential kinetic freeze-out.It is also observed that the peripheral nucleus–nucleus(AA)and pp collisions at the same center-of-mass energy per nucleon pair are in good agreement in terms of the extracted parameters.

Event patterns from negative pion spectra in proton-proton and nucleus-nucleus collisions at SPS

Rapidity-dependent transverse momentum spectra of negatively charged pions measured at different rapidities in proton-proton collisions at the Super Proton Synchrotron （SPS） at various energies within its Beam Energy Scan （BES） program are investigated by using one- and two-component standard distributions where the chemical potential and spin property of particles are implemented. The rapidity spectra are described by a double- Gaussian distribution. At the stage of kinetic freeze-out, the event patterns are structured by the scatter plots in the three-dimensional subspaces of velocity, momentum and rapidity. The results of the studies of the rapidityindependent transverse mass spectra measured at mid-rapidity in proton-proton collisions are compared with those based on the similar transverse mass spectra measured in the most central beryllium-beryllium, argon-scandium and lead-lead collisions from the SPS at its BES energies.

Universal scaling of kinetic freeze-out parameters across different collision systems at LHC energies

In this study,we perform Tsallis Blast-Wave analysis on the transverse momentum spectra of identified hadrons produced in a wide range of collision systems at the Large Hadron Collider(LHC) including pp,pPb,XeXe,and PbPb collisions.The kinetic freeze-out properties varying with event multiplicity are investigated across these systems.We find that the extracted kinetic freeze-out temperature,radial flow velocity,and non-extensive parameter exhibit a universal scaling behavior for these systems with very different geometric sizes,especially when the independent baryon Tsallis non-extensive parameter is considered.This universality may indicate the existence of a unified partonic evolution stage in different collision systems at the LHC energies.