PT spectra in pp and AA collisions at RHIC and LHC energies using the Tsallis-Weibull approach

Abstract

The Tsallis q -statistics have been incorporated in the Weibull model of particle production, in the form of q-Weibull distribution, to describe the transverse momentum ( $p_{T}$ ) distribution of charged hadrons at mid-rapidity, measured at RHIC and LHC energies. The q-Weibull distribution is found to describe the observed $ p_{T}$ distributions over all ranges of measured $ p_{T}$ . Below 2.2 GeV/c, while going from peripheral to central collisions, the parameter q is found to decrease systematically towards unity, indicating an evolution from a non-equilibrated system in peripheral collisions, towards a more thermalized system in central collisions. However, the trend is reversed in the all inclusive $ p_{T}$ regime. This can be attributed to an increase in relative contribution of hard pQCD processes in central collisions. The $ \lambda$ -parameter is found to be associated with the mean $ p_{T}$ or the collective expansion velocity of the produced hadrons, which shows an expected increase with centrality of collisions. The k parameter is observed to increase with the onset of hard QCD scatterings, initial fluctuations, and other processes leading to non-equilibrium conditions.