Kinetic freeze-out temperatures in central and peripheral collisions:which one is larger?

摘要

The kinetic freeze-out temperatures, T_0, in nucleus–nucleus collisions at the Relativistic Heavy Ion Collider(RHIC) and Large Hadron Collider(LHC) energies are extracted by four methods:(1) the Blast-Wave model with Boltzmann–Gibbs statistics(the BGBW model),(2) the Blast-Wave model with Tsallis statistics(the TBW model),(3) the Tsallis distribution with flow effect(the improved Tsallis distribution), and(4) the intercept in T=T_0+ am_0(the alternative method), where m_0 denotes the rest mass and T denotes the effective temperature which can be obtained by different distribution functions. It is found that the relative sizes of T_0 in central and peripheral collisions obtained by the conventional BGBW model which uses a zero or nearly zero transverse flow velocity, β_T, are contradictory in tendency with other methods. With a re-examination for β_Tin the first method,in which β_Tis taken to be ～ (0:40 ± 0:07)c, a recalculation presents a consistent result with others. Finally, our results show that the kinetic freeze-out temperature in central collisions is larger than that in peripheral collisions.