Statistical fragmentation of Au projectiles atE/A=600 MeV

Abstract

The mean multiplicity of intermediate mass fragments (IMF) (M«") produced by fragmentation of Au projectiles interacting with targets of C, Al, Cu, and Pb at an incident energy of E/A =600 MeV is compared to predictions of statistical multifragmentation and sequential evaporation models. The initial conditions for the calculations were provided by Boltzmann-Uehling-Uhlenbeck simulations. In the high excitation energy regime where the IMF multiplicity reaches its maximum the observed universal correlation between (M«") and the total charge Zb, ""~o f projectile fragments with charges Z~2 cannot be reproduced by a sequential evaporation code. In this regime the data are better described by statistical decay calculations which assume the formation of an expanded nuclear system and a rather fast breakup.

Liquid-Gas Phase Transition in Nuclear Multifragmentation

“…Independent of different analysis methods, densities lower than 1/3 of the normal nuclear matter density provide the best agreement with the data. Consistent with such a conjecture, models that assume normal nuclear matter density underpredict the fragment multiplicities [37,[52][53][54].…”

Statistical description of nuclear break-up

“…For example, this follows from the fact that a popular sequential GEMINI code cannot describe the multifragmentation data [20,21,22]. We believe that a formal reason of this failure is that the evaporation approaches always predict larger probabilities for emission of light particles (in particular, neutrons) than for intermediate mass fragments (IMFs).…”

Multifragmentation in Heavy-Ion Processes

“…For this, they must rely on a separate dynamical calculation (98,99,112,117), or they are used with the excitation~ energy as a free parameter (113,114,118). This severe limitation is shared with other · "equilibrium" models, e.g.…”

“…Sometimes this theory is grafted to the end of a dynamical theory that provides, somehow, information about the number of broken bonds (92)(93)(94)(95)(96)(97)(98)(99). Remarkably, this theory predicts many features of the experimentally observed mass distributions and fragment multiplicities.…”