Dynamical fission of the quasiprojectile and isospin equilibration for the system Kr80+Ca48 at 35 MeV/nucleon

Abstract

Experimental results concerning the dynamical fission of quasiprojectiles in semiperipheral collisions for the system 80 Kr+ 48 Ca at 35 MeV/nucleon are presented. Data have been collected with four blocks of the FAZIA setup in the first physics experiment of the FAZIA Collaboration. The degree of isospin equilibration between the two fission fragments and its dependence on their charge asymmetry is investigated. The data are compared with the results of the AMD model coupled to GEMINI as an afterburner, in order to get hints about the timescale of the process.

Isospin transport phenomena for the systems Kr80+Ca40,48 at 35 MeV/nucleon

“…1 of Ref. [40]. From the comparison 237 of the experimental results with the prediction of this model, 238 some hints toward a stiff symmetry energy have been found 239 (see Sec.…”

“…[38,39] and references therein), with extremely good capabilities in terms of isotopic identification (up to Z = 25 for ejectiles punching through the first 300-μm-thick silicon layer and up to Z = 20 for particles stopped in the first layer), can be very useful in shedding further light on the isospin transport phenomena and in better constraining the density dependence of the symmetry energy term; in fact, also in a reduced configuration, as the one used for the experiment described in this work, FAZIA is able to add new experimental data on this topic to the 1 The symmetry energy is commonly expanded aroung ρ 0 as [23]; the models for the symmetry energy are defined as stiff or soft depending on the value of the slope parameter L. large amount of already published measurements. In this pa-227 per we report the experimental results concerning the isospin 228 transport for the systems 80 Kr + 40,48 Ca at 35 MeV/nucleon 229 using experimental data collected with a reduced setup (four 230 blocks) during the first FAZIA experiment; this data set is the 231 same analyzed in Ref. [40].…”

“…In this pa-227 per we report the experimental results concerning the isospin 228 transport for the systems 80 Kr + 40,48 Ca at 35 MeV/nucleon 229 using experimental data collected with a reduced setup (four 230 blocks) during the first FAZIA experiment; this data set is the 231 same analyzed in Ref. [40]. The event selection criteria have 232 been checked by means of a transport model (antisymmetrized 233 molecular dynamics AMD [41][42][43]) coupled with the statis-234 tical code GEMINI [26,28,44] as an afterburner, which was 235 able to well reproduce the main features of the experimental 236 events, as shown in Fig.…”

“…As described in Ref. [40], the experiment took place at 242 INFN-LNS, with a beam of 80 Kr at 35 MeV/nucleon, deliv-243 ered by the Ciclotrone Superconduttore (CS) cyclotron with 244 an average current of 0.1 pnA, impinging on either of two 245 500-μg cm −2 -thick Ca targets, a neutron-deficient 40 Ca and a 246 neutron-rich 48 Ca. Both targets were sandwiched between two 247 thin (10-μg cm −2 -thick) layers of 12 C to avoid prompt oxida-248 tion.…”

“…The choice of a beam with N/Z = 1.22, in between that 249 of both calcium targets (1.0 and 1.4), was specifically adopted 250 to investigate the isospin transport looking at the properties 251 of the QP residue and its decay products after reacting with 252 a more or less neutron-rich target. Unfortunately the quality 253 of the data collected with the 40 Ca target is worse because a 254 parasitic beam of 40 Ar at the same beam energy was delivered 255 together with the 80 Kr beam; this fact requires more stringent 256 conditions for the selection of the QP residue coming from the 257 80 Kr beam, for example a very high lower limit (Z > 18) on 258 the size of the QP residue when the 40 Ca case is analyzed, thus 259 rejecting the most dissipative events. The choice of Z = 19 as 260 a lower limit for the QP residue is sufficient to exclude the 261 pollution due to the 40 Ar (Z = 18) parasitic beam; in fact, as 262 it will be shown in Sec.…”