Universal pion freeze-out phase-space density

Abstract

Results on the pion phase-space density at freeze-out in sulphur-nucleus, Pb-Pb and π-p collisions at the CERN SPS are presented. All heavy-ion reactions are consistent with the thermal Bose-Einstein distribution f = [exp(E/T ) − 1] −1 at T ∼ 120 MeV, modified for radial expansion. π-p data are also consistent with f , but at T ∼ 180 MeV and without radial flow.

Fluctuations in non-ideal pion gas with dynamically fixed particle number

“…We consider this relation as an equation for n a (µ + , µ − ). Then we can calculate derivatives in (15). On the other hand, the system of equations (4) implicitly defines functions µ a = µ a (n + , n − ).…”

“…The magnitude of the chemical potential depends on how medium flow [13] and resonance con-tributions [14] are included. Subsequent more detailed analyzes of the SPS data [15,16], using the method proposed in [17] of extraction of the pion freeze-out space density from the mid-rapidity particle densities and the femtoscopic radii, showed its significant enhancement at small transverse momenta.…”

Rapidity dependence of deuteron production in centralAu+Aucollisions atsNN=Arsene1, Bearden2, Beavis3 et al. 2011Phys. Rev. C20020View full textAdd to dashboardCite

“…At AGS energies f at m T = 0 is 10 times bigger than its value at RHIC, while at SPS it is 2 times bigger. In contrast, the pion average phase-space density has the opposite behavior as the energy of the colliding system increases; the values at RHIC [39] are higher than those at SPS by a factor ∼ 2 where f = 0.45 [55]. At √ s NN 4.9 GeV f was extracted from HBT and spectra measured at high rapidity y ∼ 3.1 in Au+Au 10% central collisions and its estimated value at midrapidity is ∼ 5 times smaller that the RHIC value [22].…”