Fragmentation Of ⁴⁰Ar On CH₂ Target At 500 A MeV

The study of nuclear fragmentation at medium and high energy levels has always been a frontier topic in nuclear physics.It has laid an important foundation for cosmic ray propagation,radiation protection and cancer treatment by heavy ions.In recent years,it also provides important parameters for the measurement of nuclear radius.Therefore,it is necessary to study the nuclear reaction induced by middle and high energy heavy ions.In this work,the total charge-changing cross sections,the partial cross sections,the emission angle distribution of projectile fragments（PFs）,the transverse momentum distribution of projectile fragments（PFs）and the temperature of PF emission sources for fragmentation of ⁴⁰Ar on polyethylene target（CH₂）at the highest energy of 500 A MeV are investigated and the latest experimental data are given,using a CR-39 plastic nuclear track detector.It is found that the total charge-changing cross sections for fragmentation of ⁴⁰Ar on CH₂ targets are independent on the beam energy in our studied energies,and are consistent with the experimental data of other experimental groups and the predictions of Bradt-Peter semi-empirical formula,Nilsen parameterized formula,NUCFRG2 and PHITS theoretical simulation codes within the error range.The partial cross sections increase with the increase of the charge of PF（6≤Z≤17）for the same target.The partial cross sections for projectile fragment production are independent on beam energy in our studied energies for each targets and do not show a significant even-odd effect,The partial cross sections is in good agreement with the theoretical prediction of Cummings When the charge change is small.The results show that the scattering angle of primary particles is obviously smaller than that of secondary particles,and the distribution width of scattering angle of primary particles is obviously smaller than that of secondary particles;The averaged emission angle decrease with the increase of the charge of PF for the same target,and no obvious dependence of angular distribution on the beam energy is found for the same PF.It is found that the average transverse momentum decrease with the increase of the charge of PF for the same target,and no obvious dependence of transverse momentum distribution on the beam energy is found for the same PF.The cumulated squared transverse momentum distribution of PF can be well explained by a single Rayleigh distribution,the temperature parameter of PFs emission source is obtained,which is about 0～9.0 MeV and do not depend on the beam energy for PF with charge of 6≤Z≤17.In addition,the temperature of PFs emission source decrease with the increase of the charge of PF for the same target,which is about 0～6.0 MeV.