Light charged particles emitted in fission reactions induced by protons onPb208

Abstract

Light charged particles emitted in proton-induced fission reactions on 208 Pb have been measured at different kinetic energies: 370A, 500A, and 650A MeV. The experiment was performed by the SOFIA Collaboration at the GSI facilities in Darmstadt (Germany). The inverse kinematics technique was combined with a setup especially designed to measure light charged particles in coincidence with fission fragments. This measurement allowed us, for the first time, to obtain correlations between the light charged particles emitted during the fission process and the charge distributions of the fission fragments. These correlations were compared with different model calculations to assess the ground-to-saddle dynamics. The results confirm that transient and dissipative effects are required for an accurate description of the fission observables.

Microscopic description of proton-induced spallation reactions with the constrained molecular dynamics (CoMD) model

“…Similar comparisons can be performed for the multiplicities and the spectra of emitted protons and other light charged particles in conjunction with recent experimental data (e.g. [70,71]). This is the subject of ongoing systematic efforts in our group.…”

Constraint of the Nuclear Dissipation Coefficient in Fission of Hypernuclei

“…2 to illustrate the evolution with the presence of Λ hyperons in the nuclear system. Here we believe the nuclear dissipation coefficient is well constrained for normal nuclear matter taking into the large number of nuclear fission experiments performed in the last decades, so the value of ð4.5 AE 2.0Þ × 10 21 s −1 is quite robust [31,32,[32][33][34][35]61,62]. Applying the same calculations to hypernuclear matter we find that the value of the dissipation coefficient increases roughly a factor of 6 due to the presence of a Λ hyperon and the linear extrapolation of our findings to a larger number of Λ hyperons leads to higher dissipation coefficients, for instance, β ¼ 75 × 10 21 s −1 for hypernuclei containing three Λ hyperons.…”

“…Measurement of other fission observables, such as the charge and mass distributions of the fission fragments as well as the multiplicity of emitted particles, in combination with relativistic proton-nucleus and nucleus-nucleus [66] collisions in inverse kinematics might shed light on the dependence of the dissipation parameter with the nuclear density and nuclear deformations, as already investigated with normal nuclei [33][34][35]62]. Moreover, the measurement of double-Λ hypernuclei fission reactions could be used to constrain the dissipation coefficient at a larger number of Λ hyperons and to better understand the tendency shown in the Fig.…”

“…In this Letter, we propose to investigate the dissipation coefficient in hypernuclear matter following the methodology proposed in pioneering works on nuclear fission, in which fission cross sections [31,32], charge distribution of fission fragments [32][33][34], multiplicity of γ rays, neutrons, and light-charged particles [9,35] were used to obtain the nuclear dissipation coefficient in normal nuclear matter. For the present work we take advantage of the data collected during the hypernuclei experiments [36,37] performed at the COSY-Jülich facility (Germany) by comparing the fission cross sections induced in heavy hypernuclei to dynamical calculations based on the FPE approach, which also allows us for the first time to study the dependence of the dissipation parameter on the number of hyperons that constitute the nuclear system.…”

“…The comparison allowed us to constrain the dissipation parameter in fission of hypernuclear matter, resulting in an average value of ð28 AE 12Þ × 10 21 s −1 [63]. This finding is 6 times larger than that obtained for normal nuclear matter [10,31,32,35,61,62], which implies that in the presence of hyperons the conversion of intrinsic energy into collective motion goes much slower.…”