Study On The Distribution Of Neutron-proton Chemical Potential In Neutron-rich Heavy-ion Reactions

Nuclear symmetry energy,known as an important parameter of nuclear equation of state,has been a hot topic in nuclear physics.The study showed that the symmetry energy depends on both density and temperature,and present research indicates that the isobaric yield ratio difference（IBD）is sensitive to nuclear density.Therefore we use the IBD method to study nuclear symmetry energy.In this thesis,comparing the product results between simulation models in the intermediate energy heavy-ion collisions（HICs）and the target effects in the IBD results have been mainly studied.The first section,we have been used the antisymmetrized molecular dynamics（AMD）model,the modified statistical abrasionablation（SAA）model,and the empirical formulae（EPAX）to calculate the cross sections of fragments in the 140 AMeV ^58,64Ni+⁹Be reactions.Results of all the simulation models have been compared with the experimental datas,and then obtained the predictive ability of different models by using the comparison results in the HICs.In the research,the IBD has been proposed as a new probe for nuclear density and chemical potentials of neutrons and protons.Thus,it is an important task to reproduce the cross sections of fragments.In the second section,we have been used the isoscaling method to analyze the 140 AMeV^40,48Ca+¹⁸¹Ta/9Be and 58,64Ni+181Ta/9Be reactions.Then,an IBD method has been proposed to research the ratio of the difference between the chemical potential of neutron and proton to temperature（? ?）.Though comparing the results of the IBD method with the isoscaling（IS）method in the 140 AMeV^40,48Ca+¹⁸¹Ta/9Be and 58,64Ni+181Ta/9Be reactions,we discussed and analyzed the similarity degree of the different methods.It showed that the IBD is a new probe for chemical potential of neutrons and protons or nuclear density.The IBD between reactions has been found to be sensitive to the density difference between projectiles in the Fermi energy HICs,and then studied the target effects in the isobaric yield ratio（IYR）and the IBD results.The data with high precision of the 140 AMeV^40,48Ca+¹⁸¹Ta/9Be and ^58,64Ni+¹⁸¹Ta/9Be has been measured,and calculated the IYR and IBD methods which from these reactions to research the effects of the light 9Be and heavy ¹⁸¹ Ta targets.The difference（?）and ratio（?）between the IBD results for the reactions with Ta and Be targets was defined to quantitatively show the target dependence of the IBD results respectively.The IYR’s results of reactions with symmetric projectiles are more easily affected than those for reactions with neutron-rich projectiles.The IBD results were suppressed by using the 181 Ta target in different degrees.