Extractions Of The Nuclear-matter Density Distributions Of Some Exotic Nuclei (^12,14Be、⁸B) And Their Applications

In the1980s, since the rapid developments of the techniques of the acceleratorand detector, a series of peculiarities of exotic nuclei are revealed by bombarding sta-ble nuclei with radioactive ion beam. New methods and theoretical models are broughtup to study the internal structure. Measuring the nuclear reaction cross section σRcombining Glauber model is one of the most basic and mature approaches. Recently,M. Fukuda has improved traditional Glauber model and develop a a Modified Opti-cal Limit Glauber model (MOL[FM]). The MOL[FM] has reduced the discrepancybetween the calculation and data to be only about1-2%for the energy region fromseveral tens of MeV/nucleon to1GeV/nucleon. By measuring the σRon Be, C, Altargets at intermediate energies, the nuclear-matter density distributions of8Li,17Neand22C have been determined accurately with MOL[FM]. Hence measuring the σIor σRand determine the nuclear-matter density distribution with MOL[FM] is still amore mature and promising method at present. Therefore, we are motivated to studyseveral interesting exotic nuclei12,14Be and8B by the method.First,12Be is just an interesting combination of the peculiarities of exotic nuclei.In the last decade a bunch of excellent works on12Be have emerged. And the study inthe12Be ground state structure especially in the configuration attracts much attention.At present there is still debate on the problem that whether the ground state configu-ration of(12)Be is dominated by the p-wave or the s component. The controversy canprobably be settled through the determination of the nuclear-matter density distribu-tion of12Be. Considering that the current experimental result is not accurate enoughto precisely extract the ground state configuration of12Be, more experimental researchon the nuclear-matter density distribution of12Be is desirable. Refer to14Be, the exist-ing data can not provide sufcient information to exactly determined the ground statestructure of14Be. And the extraction of the nuclear-matter density distribution of14Becan provide complementary information for determining whether the ground state of14Be is’a core+2neutron’ or’a core+4neutron’. Plus nuclear-matter density dis-tribution of14Be can be possibly used to study the diference between the12Be core in 14Be and the free12Be.As for8B, its β+decay is the major source of high energy solar neutrino. The7Be(p,γ)8B capture reaction is the key to solve the high energy solar neutrino problem.The flux of the high energy solar neutrino is directly proportional to the cross sectionfactor S717(E) ofBe(p,γ)8B capture reaction at low-energy region (Ec.m.=20keV).Though a lot of experimental data have been attained in the recent half century, theyare all above100keV, and the S17(E) at low energy region is still not available throughmeasurement. Hence in the energy region of astrophysical interest (several tens ofkeV), the extrapolation from the data at high energy region is the only way to obtainthe S17(E). And there exists divergence of above20%between the extrapolations fromdiferent models, which makes S17(0) still the most uncertain input parameter in solarmodels. Within the direct radioactive capture model, the initial state and the operatorare so simple and clear that the only ambiguous parameter is the final state. Hence thedensity distribution of8B, which directly corresponds to the final state wave function,is very important.Therefore we bring forward to study12,14Be and8B by measuring the σRanddetermining their nuclear-matter density distributions with MOL[FM]. In this work,firstly we carefully studied the feasibility of measuring the σRof12,14Be on C andAl at about30-50MeV/nucleon, and give detailed experimental scheme after opti-mization. Then by using existed interaction cross section data of12Be on C at790MeV/nucleon and MOL[FM], the upper limit of the s orbital occupation probabil-ity of12Be ground state is roughly determined to be56%with Single Particle Model(SPM) calculations. This demonstrates that the method is very promising to deter-mine the s orbital component of12Be with proper nuclear-matter density distributioncalculations for diferent orbital of12Be ground state. The precision of the s orbitaloccupation probability of12Be ground state is expected to achieve9%by using theproposed data. Secondly, base on the data of σ8RofB on Be, C and Al at around30-110MeV/nucleon obtained by M. Fukuda group in Osaka university, we extractthe nuclear-matter distribution of8B by using Harmonic Oscillator distribution andYukawa function.Besides this work, we have performed an experimental study for measuring the decay branching ratio of the nuclear state in189Os nucleus. We put forward an exper-imental method to measure the branching ratio. The feasibility for the measurementis verified through theory analysis and a preparation experiment on the experimentalstation BL13W1in Shanghai Synchrotron Radiation Facility (SSRF).