Phenomenology of flow disappearance in intermediate-energy heavy ion collisions

Abstract

The disappearance of collective flow effects in heavy ion collisions is investigated using a microscopic optical model formalism for estimating collision momentum transfers. Phenomenological expressions for the balance energy are obtained which agree very well with measurements for various experimental collision pairs and with results obtained from Boltzmann-Uehling-Uhlenbeck simulations.

Collective Flow in Heavy-Ion Collisions

“…Since then many theoretical works concerned with the disappearance of flow have appeared (101,119,(135)(136)(137)(138)(139)(140)(141)(142)(143)(144)(145)(146)(147). These calculations all confirm the findings just mentioned.…”

Systematic study of the energy of vanishing flow using IQMD model and comparison with various theoretical models

“…Another attempt to calculate the EVF was made within AMD model by Ono et al [27] for the reactions of 12 4, but for (a) UrQMD calculations by Guo et al [28], (b) AMD calculations by Ono et al [27] and (c) optical model calculations by Tripathi et al [36]. Fit in (c) is between mass 67 to 394 units.…”

“…In the last part of the comparison, we display the results of optical model calculations by Tripathi et al [36] (figure 5(c)). From the figure, we see that EVF in medium and heavy mass reactions is nearly the same in both models whereas lighter masses have different energies of vanishing flow.…”

“…The energy of vanishing flow (EVF), where attractive and repulsive interactions counterbalance each other [13], is of particular significance since it can be directly compared with theoretical models. Up to now, one has measured the EVF in the reactions of 12 C+ 12 C [4], 20 Ne+ 27 Al [4], 36 Ar+ 27 Al [14,15], 40 Ar+ 27 Al [16], 40 Ar+ 45 Sc [4,6,19], 40 Ar+ 51 V [13], 64 Zn+ 27 Al [17], 40 Ar+ 58 Ni [18], 64 Zn+ 48 Ti [15], 58 Ni+ 58 Ni [11,18,19], 58 Fe+ 58 Fe [11,19], 64 Zn+ 58 Ni [15], 86 Kr+ 93 Nb [4,19], 93 Nb+ 93 Nb [13], 129 Xe+ 118 Sn [18], 139 La+ 139 La [13], and 197 Au+ 197 Au [3]. Most of these measurements were done for the central collisions only.…”

“…C+12 C ( b = 0.4),20 Ne+27 Al ( b = 0.4),36 Ar+ 27 Al (b = 0−2.5 fm), 40 Ar+ 27 Al (b = 1.6 fm), 40 Ar+ 45 Sc ( b = 0 − 0.28), 40 Ar+ 51 V ( b = 0.3), 64 Zn+ 27 Al (b = 0−2 fm), 40 Ar+ 58 Ni (b = 0−3 fm), 64 Zn+ 48 Ti (b = 0−2.5 fm), 58 Ni+ 58 Ni ( b = 0−0.28), 64 Zn+ 58 Ni (b = 0−2.5 fm), 86 Kr+ 93 Nb ( b = 0−0.28), 93 Nb+ 93 Nb ( b = 0.3), 129 Xe+ 118 Sn (b = 0−3 fm), 139 La+ 139 La ( b = 0.3), and 197 Au+ 197 Au (b = 0−4 fm) as per experimental measurements…”