Isoscaling and nuclear reaction dynamics

Abstract

Isoscaling parameters α and β have been explored as a function of breakup angle in binary excited projectile-like fragment decays produced in collisions of 70 Zn + 70 Zn and 64 Zn + 64 Zn at 35 MeV per nucleon. In this analysis, focus was placed on isoscaling the second heaviest fragment with 4 ≤ ZL ≤ 8 emitted from the excited projectile-like fragment in events that contained a heavy fragment with ZH ≥ 12. The breakup orientation θprox was defined as the angle between the heavy and light fragments' center of mass velocity and the fragment pairs' relative velocity. Breakups between 0 • < θprox ≤ 80 • have been shown to be dominated by dynamical contributions, while break-up angles of θprox > 100 • are predominantly statistical. Historically, isoscaling has often been understood and applied in a statistical context, assuming that the fragments are produced after statistical equilibrium is achieved. Studying isoscaling parameters as a function of θprox reveals the sensitivity of α and β to the mechanism of fragment production.

Characterization of the breakup channel in the asymmetric systems $^{40,48}$Ca+$^{12}$C at 25 and 40 MeV/nucleon

“…E * = E rel − Q value 8The obtained value around 0.5 MeV is slightly below the expected one of 0.67 MeV; the expected value is calculated fromE * = E * 9 Be − Q9 Be→ 8 Be+n − Q8 Be→α+α .This shift may be due to a deformation of the excitation energy spectrum caused by a defective production of the uncorrelated yields 9. The decay of9 Be from the level at 1.68 MeV (with 100% probability of neutron decay) falls in the region of the8 Be ground state and it cannot be resolved, thus acting as a further background for this state.10 E * 12C = 3 i=1 E i − Q12 C→3α, where E i is the kinetic energy of the i th α calculated with respect to the c.m. of the 3 α…”

“…As discussed in the literature [50] it mainly corresponds to the incomplete reconstruction of the excited 9 Be (energy level: 2.43 MeV 8 ) for which the free neutron is not detected; it is reasonable that its contribution is larger for the neutron rich 48 Ca reactions; its population also decreases passing from 25 to 40 MeV/nucleon 9 . The presence of the second excited state 2 + at 3.03 MeV of 8 Be is masked by the background due to incompletely reconstructed 12 C * nuclei decaying into 3 α, as shown in the bottom inset of Fig. 14 for the system 48 Ca at 25 MeV/nucleon.…”

“…The investigation of the breakup channel in heavy ion collisions at Fermi energies is a topic widely represented in the literature since many years. In particular, efforts have been done to study the emission pattern of the frag-ments coming from the QuasiProjectile (QP) breakup [1][2][3][4][5][6][7][8][9][10]. For example, one goal is the investigation of the differences between this process and a pure low-energy fission modelized in terms of the nuclear structure and statistical arguments.…”

Dense Nuclear Matter Equation of State from Heavy-Ion Collisions

“…The technique of equilibration chronometry allows the visualization of the time evolution of the neutron excess. Signatures of neutron-proton equilibration obeying first-order kinetics are observed both in experimental data [395][396][397][398] and in transport calculations [399]. Since the equilibration depends on the neutron and proton chemical potentials, this technique offers new experimental data to constrain the sub-saturation EOS through comparisons with simulations [6,47,400].…”

Isoscaling properties for neutron-rich fragments in highly asymmetric heavy ion collision systems*

“…Some experimental observations suggested a strong decrease in isoscaling parameters with increasing centrality to values smaller than 50% of those obtained for the peripheral groups [17]. Additionally, it was shown that the isoscaling parameters were different for emitted and projectilelike fragments [18]. Various molecular dynamics simulation studies have shown that isoscaling parameters vary wildly with the evolution of the reaction system [19].…”