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Tsallis statistics was used to investigate the non-Boltzmann distribution of particle spectra and their dependence on particle species and beam energy in the relativistic heavy-ion collisions at SPS and RHIC. Produced particles are assumed to acquire radial flow and be of non-extensive statistics at freeze-out. J/ψ, and the particles containing strangeness were examined separately to study their radial flow and freeze-out. We found that the strange hadrons approach equilibrium quickly from peripheral to central A+A collisions and they tend to decouple earlier from the system than the light hadrons but with the same final radial flow. These results provide an alternative picture of freeze-outs: a thermalized system is produced at the partonic phase; the hadronic scattering at a later stage is not enough to maintain the system in equilibrium and does not increase the radial flow of the copiously produced light hadrons. The J/ψ in Pb+Pb collisions at SPS is consistent with early decoupling and obtains little radial flow. The J/ψ spectra at RHIC are also inconsistent with the bulk flow profile.

Nonextensive statistics in a Blast-Wave model (TBW) is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the Number of Constituent Quark Scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation and the suppression of hadron production at high transverse momentum (p T ) due to jet quenching. In this formalism, the NCQ scaling at RHIC appears as a consequence of non-equilibrium process. Our study also provides concise reference distributions with a least χ 2 fit of the available experimental data for future experiments and models. Keywords:Tsallis Statistics, non-equilibrium, nonextensive, Quark-Gluon Plasma, Constituent Quark Scaling, perfect liquid, anisotropic flow, jet quenching, Blast-Wave model Several intriguing features were discovered in relativistic heavy ion collisions [1, 2, 3, 4] when particles emerging from the Quark-Gluon Plasma were detected by the experiments at RHIC. In Au+Au collisions, identified particle yields integrated over the transverse momentum range around the center-of-mass rapidity window have been shown to be at equilibrium at the chemical freeze-out in a statistical analysis [1,5]. The hydrodynamic model with proper equation of state and initial condition can describe the anisotropic flow with small shear viscosity and provides the notion of "perfect liquid" [6,7]. Furthermore, the transverse momentum distributions of identified particles can be described in a hydrodynamic-inspired model with a compact set of parameters [1,5,8,9,10].However, in the intermediate p T range, particle production exhibits grouping between baryons and mesons with baryons having relatively higher yield and larger elliptic flow than the mesons [1,11]. This feature of constituent quark scaling is not present in the hydrodynamics. A microscopic quark coalescence at the hadronization seems to be inescapable [4,12]. At even higher p T , hard perturbative QCD processes (jets) are relevant. Absorption of jets in the medium formed in A+A collisions has been used for studying the properties of the QGP [3,13,14]. Even though hydrodynamics with space-time evolution from an initial condition [6] is so far the most realistic simulation for bulk matter produced in relativistic heavy ion collisions, its applicability is expected to breakdown for p+p and peripheral A+A collisions at RHIC. Recent study Email address: zbtang@ustc.edu.cn (Zebo Tang) showed that hydrodynamics can not replace the microscopic hadronic cascade at the late stage regardless of freeze-out and equation of state one chooses [15] because the particle interactions may be dominated by non-equilibrium hadronic processes [16]. In A+A collisions, the fluctuations at initial impact due to Color-Glass Condensate (CGC) formation or individual nucleon-nucleon co...

It has been debated for decades whether hadrons emerging from p+p collisions exhibit collective expansion. The signal of the collective motion in p+p collisions is not as clear/clean as in heavy-ion collisions because of the low multiplicity and large fluctuation in p+p collisions. Tsallis Blast-Wave (TBW) model is a thermodynamic approach, introduced to handle the overwhelming correlation and fluctuation in the hadronic processes. We have systematically studied the identified particle spectra in p+p collisions from RHIC to LHC using TBW and found no appreciable radial flow in p+p collisions below √ s = 900 GeV. At LHC higher energy of 7 TeV in p+p collisions, the radial flow velocity achieves an average value of β = 0.320 ± 0.005. This flow velocity is comparable to that in peripheral (40-60%) Au+Au collisions at RHIC. Breaking of the identified particle spectra mT scaling was also observed at LHC from a model independent test.