Nuclear Fireball Model for Proton Inclusive Spectra from Relativistic Heavy-Ion Collisions

Abstract

A simple model is proposed for the emission of nueleons with velocities intermediate between those of the target and projectile. In this model, the nueleons which are mutually swept out from the target and projectile form a hot quasiequilibrated fireball which decays as an ideal gas. The overall features of the proton-inclusive spectra from 250-and 400-MeV/nucleon 20 Ne ions and 400-MeV/nucleon 4 He ions interacting with uranium are fitted without any adjustable parameters.

Nuclear stopping and light charged particle emission in C12+C12 at 95 MeV/nucleon

“…Westfall et at., pointed out that the IV source of proton spectra can be described by a fireball model at incident energies above 200 MeV/nucleon [10]. The fireball model is commonly accepted for the production mechanism of the IV source of LCPs at the BEVALAC energy, based on the experimental data of the pioneering works at LBL [11,12]. Below 200 MeV/nucleon, notable deviations from the fireball picture have been reported [10,13,14].…”

Progress in Collective Flow Studies from the Onset to Bevalac/SIS

“…In the simple thermodynamic "fireball', model [40], one assumes a non-isentropic expansion resulting in transverse momentum spectra that are, in the classical limit, of Maxwell-Boltzmann type, the inverse exponential slope representing the source temperature T. If, on the other hand, the decay resembles more hydrodynamic expansion, due to a short mean free path of escaping nuclear matter, one would expect a "shoulder arm" on the spectra resulting from the ordered radial motion, or "blast wave." The shape of the spectra then would be dictated by the radial flow velocity ,f?…”

Towards relativistic heavy ion collisions “by small steps towards the stars”

“…The initial excitation may be in the form of uncorrelated particle-hole excitations, in which case this relaxation time is related to the Fermi velocity. On the other hand, if the initial excitation is carried by coherent, collective compreseional modes, then this time is related to the frequency of these modes, which in turn depends on the speed of sound in nuclear matter (Johansen, 1977). Recent experiments (Youngblood, 1977), de termining the frequency of the monopole mode (Pandharpande, 1970) lead to a value of the compressibility coefficient K == 300 MeV, and an implied velocity of sound V g = •K/9m of 0.19 c (m is the nucleon rest mass).…”