Fragmentation of gold projectiles: From evaporation to total disassembly

Abstract

We have studied the fragmentation of Au projectiles interacting with targets of C, A1 and Cu at an incident energy of E/A = 600 MeV. The employed inverse kinematics allowed a nearly complete detection of projectile fragments with charge Z > 2. The recorded fragmentation events were sorted according to three observables, the multiplicity Mtp of light charged particles, the largest atomic number Zma x within an event, and a new observable, Zbound, representing the sum of the atomic numbers Z of all fragments with Z>__ 2. Using these observables, the impact parameter dependence of the fragmentation process was investigated. For all three targets, a maximum mean multiplicity of 3 to 4 intermediate mass fragments (IMFs) is observed. The corresponding impact parameters range from central collisions for the C target to increasingly peripheral collisions for the heavier targets. It is found that the correlation between the IMF multiplicity and Zbouna, extending from evaporation type processes (large Zbouna) to the total disassembly of the projectile (small Zbound) , is independent of the target nucleus. This universal behaviour may suggest an -at least partial -equilibration of the projectile fragment prior to its decay.

Angular patterns from fragments produced in central heavy-ion collisions

“…Furthermore, the good overall agreement between the information about density shapes can be equally well obtained from analyses in either respectively. In spite of some discrepancies, these calculations seem to indicate that obtained according to (i), while the open circles and squares correspond to (ii) and (iii), per nucleon) + AgBr [1,6,22,23]. The full symbols in this picture represend the results nucleon) + AgBr [7,21], Ar (65 MeV per nucleon) + AgBr [6,21,22], and O (210 MeV angular pattern suggested by the multipolarity coeiiicients shown in Fig.…”

“…Thus, our results seem to favor a soft equation of state for this reaction and already reported in ref. [6], the hypothesis of disk shaped densities sembles should be strongly dependent on the equation of state for nuclear matter, as OCR Output Furthermore, since the shape of the density at the moment at which the system disas limitations that would certainly distort the behavior of the multipolarity coefficients.…”

“…We shall come back to OCR Output the fact that bmax z 1.5 fm gives only an estimate of the maximum impact parameter per nucleon) + AgBr, we are going to consider below. Thus one should bear in mind for reactions at lower energies [6,24], such as Ar(65 MeV per nucleon) and Kr(95 MeV reliable method for high energy hea.vy-ion collisions [24], but it is not very well suited associated with the central events we are going to discuss is bmax z 1.5 fm. This is a therein).…”

“…This parameter is defined as ,8 = (A1 -A2)/(A] + (i) No heavy remnant (Z f 15), and conditions [6,22]: central events used in this analysis. They have been chosen by imposing the following can be understood by considering the criterion employed in the selection of the most there is always a privileged plane in the position space, the reaction plane, defined by OCR Output perimental observations shown in Fig.…”

Phase transitions in “small” systems – A challenge for thermodynamics

“…It was the result of experiments and theoretical thoughts especially in nuclear physics that paved the way to a new and much deeper understanding of equilibrium statistical mechanics and phase transitions in "Small" systems. I want to remind the pioneering attempts on nuclear multifragmentation, experimentally by the references [5][6][7][8][9][10][11][12][13], where finally Moretto [14] gave a concluding overview on the experimental situation of multifragmentation, even though he initially doubted the very existence of this new phenomenon in the paper entitled: "Complex fragment emission at 50 MeV/u -compound nuclei for ever" [15]. This development was soon theoretically accompanied and stimulated: [16][17][18][19][20][21][22][23][24][25][26][27][28] and others.…”