Spectra and radial flow in relativistic heavy ion collisions with Tsallis statistics in a blast-wave description

Abstract

We have implemented the Tsallis statistics in a Blast-Wave model and applied it to mid-rapidity transverse-momentum spectra of identified particles measured at RHIC. This new Tsallis Blast-Wave function fits the RHIC data very well for pT <3 GeV/c. We observed that the collective flow velocity starts from zero in p+p and peripheral Au+Au collisions growing to 0.470 ± 0.009(c) in central Au+Au collisions. The (q − 1) parameter, which characterizes the degree of non-equilibrium in a system, changes from 0.100 ± 0.003 in p+p to 0.015 ± 0.005 in central Au+Au collisions, indicating an evolution from a highly non-equilibrated system in p+p collisions toward an almost thermalized system in central Au+Au collisions. The temperature and collective velocity are well described by a quadratic dependence on (q − 1). Two sets of parameters in our Tsallis Blast-Wave model are required to describe the meson and baryon groups separately in p+p collisions while one set of parameters appears to fit all spectra in central Au+Au collisions.

Di-electron spectrum at mid-rapidity inp+pcollisions ats=200GeV

“…Table III lists the detailed systematic uncertainties for ω yields from different sources. Our ω yields from di-electron decays are consistent with previous results [49] and with a prediction from a Tsallis fit, which fits spectra of other particles and high-p T ω yields [31,44]. We obtain a mid-rapidity dN/dy of 0.10 ± 0.02 (stat.)…”

J/ψproduction at lowpTin Au + Au and Cu + Cu collisions atsNNAdamczyk1, Adkins2, Agakishiev3 et al. 2014Phys. Rev. C693420View full textAdd to dashboardCite

“…Also shown is the yield in 0%-60% centrality Cu + Cu collisions for low p T (solid triangles) and high p T [48] (open triangles). The models are described in the text [49,50]. The J /ψ cross section in p + p collisions is also shown in (d) at STAR (stars) and PHENIX [51] (diamonds), and the scale is indicated on the right axis.…”

“…However, it underestimates the yield at lower p T : χ 2 /NDF = 100/9 = 11.1 for 0 < p T < 10 GeV/c in 0%-60% central collisions. The STAR data were also fitted with a TBW model in 0 < p T < 10 GeV/c that assumes a zero radial flow velocity (solid line) [49]. Figure 10 and peripheral events (χ 2 /NDF = 2.9/9 for 20%-40% and χ 2 /NDF = 13.1/9 for 40%-60% centrality classes).…”

“…9(d) for p T < 5 GeV/c and |y| < 1 in 0%-60% centrality Au + Au and Cu + Cu collisions and compared to the high-p T J /ψ yield for Cu + Cu collisions [48] The J /ψ invariant yield in Au + Au collisions shown in Fig. 9 was compared to a Tsallis blast wave (TBW) model assuming that the J /ψ flows like lighter hadrons (dashed line) [49,50], i.e., assuming the radial flow velocity β = 0.41 for 0%-60% central collisions, 0.51 for 0%-20%, 0.44 for 20%-40%, and 0.28 for 40%-60% events. The normalization for the TBW model was determined from the high-p T data.…”

Measurements of dielectron production in Au + Au collisions atsNN=200GeV from the STAR experiment

“…Other light hadron yields include the η meson, measured by PHENIX for p T > 2 GeV/c [35], and φ meson data from STAR [36]. These hadron spectra together with hadron spectra (K ± , K 0 S , and Λ) measured by STAR and PHENIX were simultaneously fit to a core-corona based Tsallis Blast-Wave (TBW) model [37] where the core describes the Au+Au bulk production and the corona describes the hard scattering contribution from p+p like collisions.…”