Hanbury-Brown–Twiss search for new states of matter inA+Acollisions

Abstract

A method allowing studies of the hadronic matter at the early evolution stage in A+A collisions is developed. It is based on an interferometry analysis of approximately conserved values such as the averaged phase-space density (APSD) and the specific entropy of thermal pions. The plateau found in the APSD behavior vs collision energy at SPS is associated, apparently, with the deconfinement phase transition at low SPS energies; a saturation of this quantity at the RHIC energies indicates the limiting Hagedorn temperature for hadronic matter. It is shown that if the cubic power of effective temperature of pion transverse spectra grows with energy similarly to the rapidity density (that is roughly consistent with experimental data), then the interferometry volume is inverse proportional to the pion APSD that is about a constant because of limiting Hagedorn temperature. This sheds light on the HBT puzzle.

HBT and initial conditions for hydrodynamic expansion in A+A collisions

“…As a result, the phenomenological parameterizations, like the blast wave model, just ignore emission from the surface of the expanding system despite the fact that it should last at least about the extracted life-time of the fireball: 10-12 fm/c. These notes represent the possible explanation of the peculiarities of the observed behavior of the interferometry radii based on an analysis of the temporal evolution of observables [3,4]. As a result, one can conclude that initial flows in prethermal partonic matter, which precede hydrodynamical expansion, should develop in the system.…”

Pion and kaon production in centralPb+Pbcollisions at20Aand30A<

“…A minimum of the sound velocity is expected to occur in the phase transition domain. Moreover, a simultaneous analysis of the two-pion correlation function and the transverse mass spectra found a plateau in the averaged phase-space density at SPS energies which may be associated with the onset of deconfinement [31].…”

Bose-Einstein correlations ofπ−π−pairs in central Pb+Pb collisions at20A,30A

“…[50,51]. The product of the radii R side , R out , and R long is used to derive the phase-space density of the system averaged over momentum and configuration space.…”