Three large sized glass resistive plate chambers (RPCs) are built and applied to measure the spatial resolution of the detector. The readout strips are collected to a LC delay-line and the time difference is used to determine the position. Cosmic rays are triggered by a set of two scintillation counters and the coincidently measured positions from the three RPCs are used to deduce the position uncertainty. In average a spatial resolution of 0.90 mm (FWHM) is obtained for a single RPC, with a good uniformity across the detection area. This result suggests that large sized glass RPC operating in the avalanche mode is a promising candidate for the muon tomography detection system.
We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual interaction.Both particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix equation.The sensitivity of the calculated half-lives to some physical quantities used in the calculations is examined.Calculations are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = 76.Good agreement between experiment and theory is achieved especially for the nuclei far from stability,and the results of our calculations are discussed with comparison with other theoretical results.Predictions on the β-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.
Continuum discretised coupled-channels(CDCC) method with a ^(10)Be(0^+) + n two-body cluster model is applied to systematically analyze the elastic scattering of the halo nucleus ^(11)Be from the proton target at various incident energies below 100 MeV/nucleon.Using the renormalized ^(10)Be- p potential deduced from the ^(10)Be+ p elastic scattering data, the differential cross sections of ^(11)Be + p scattering are well reproduced by the CDCC calculations without any further adjustment parameters, demonstrating the applicability of this approach for describing the scattering of exotic nuclei based on the scattering of the less exotic core nuclei.
The allowed Gamow-Teller β-decay information of Li,Be,B,C,and N isotopes under the frame work of nuclear shell model is calculated herein.Theoretical results of Q values,half-lives,excitation energies,log ft values,branching fractions,and β-delayed proton/neutron emission probabilities are tabulated and compared with experimental data.The deviations from the observations are also analyzed.The 11Be nucleus is well known for its anomaly ground state Jπ=1/2+.Thus,we compared the theoretical energy levels with the experimental data and the agreements for low excitation states are consistent.The quenching factor is also evaluated and discussed.
Very neutron-deficient nuclei are investigated with Woods-Saxon potentials,especially the newly measured A =2Z-1 nucleus ^(65)As [X.L.Tu et al.,Phys.Rev.Lett.106,112501(2011)],where the experimental proton separation energy is obtained as-90(85) keV for the first time.Careful consideration is given to quasibound protons with outgoing Coulomb wave boundary conditions.The observed proton halos in the first excited state of ^(17)F and in the ground states of ^(26,27,28)P are reproduced well,and predictions of proton halos are made for the ground states of ^(56,57)Cu and ^(65)As.The sensitivity of the results to the proton separation energy is discussed in detail,together with the effect of the l=1 centrifugal barrier on proton halos.
Knockout reaction experiment was carried out by using the 6He beams at 61.2 MeV/u impinging on a CH2 target. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive meas urement the valence nucleon knockout mechanism and the core knockout mechanism can be distinguished by the relation be tween the polar angles of the core fragments and the recoiled protons, respectively. It is demonstrated that the core knockout mechanism may result in some strong contamination to the real invariant mass spectrum.
Lü LinHui1, YE YanLin1, JIANG DongXing1, HUA Hui1, ZHENG Tao1, LI ZhiHuan1, GE YuCheng1, LI XiangQing1, LOU JianLing1, CAO ZhongXin1, SONG YuShou1, XIAO Jun1, LI QiTe1, QIAO Rui1, YOU HaiBo1, CHEN RuiJiu1, XU HuShan2, WANG JianSong2, GUO ZhongYan2, ZHANG XueYing2, LI Chen2, HU ZhengGuo2, CHEN RuoFu2, WANG Meng2, XU ZhiGuo2, YUE Ke2, TANG Bin2, ZANG YongDong2, ZHANG XueHeng2, YAO XiangWu2, CHEN JinDa2 & BAI Zhen2 1 School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method,with corresponding charge density distributions from relativistic mean-field theory.The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing.The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions,though the proton numbers change uniformly in two isotonic chains.Meanwhile,the shift regularities of theminima are also discussed,and we give a clear relation between theminima of the charge form factors and the corresponding charge radii.This relation is caused by the diffraction effect of the electron.Under this conclusion,we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain.The results are also useful for studying the central depression in light exotic nuclei.
Relativistic corrections to the reaction kinematic parameters were made for elastic scattering of6Li,12C and40Ar from40Ca,90Zr and208Pb targets at incident energies between 20 and 100 MeV/nucleon.The results of optical model calculations show that the efects of such corrections are important when describing the angular distributions of elastic scattering cross sections for heavy ion scattering at incident energies as low as around40 MeV/nucleon.The efects on the total reaction cross sections on the other hand,were found to be small within the energy range studied when the optical model potential is fixed.
The Halo and cluster structure at the ground state of unstable nuclei are among the most exciting phenomena of current nuclear physics. Probing these structures requires a careful selection of reaction tools. In the past twenty years, knockout reactions have been used intensively to investigate spectroscopically the structure of unstable nuclei. In this report we have illustrated the latest development of the knockout reaction tool and have emphasized the recoiled proton tagging method. A quantitative criteria is developed to evaluate the quasi-free feature of the knockout process. The newly discovered 'towing mode' reaction tool is also outlined and its applicability at transit energies is discussed.
