Study Of Giant Resonances On Hypernuelei By Skyrme Energy Density Functional Theory

We have extended the Skyrme Hartree-Fock and Random Phase Approximation method to calculate self-consistently the multipole giant resonances of hypernuclei within the Skyrme energy density functional.Skyrme-type nucleon-hyperon and hyperon-hyperon interactions,same as nucleon-nucleon Skyrme interaction,are also adopted when we calculate the properties of ground states and excited states in hypernuclei.In the calculations we use SGII Skyrme interaction for the nucleon-nucleon interaction and No.5 for nucleon-hyperon interaction as well as the S??1 parameter set for the hyperon-hyperon interaction.First we explore the effect of hyperons on the binding energy per nucleon of nuclear matter and the giant monopole resonance(GMR),we find that the hyperon-hyperon interaction gives almost no effect,the main contribution is from hyperon-nucleon interaction,the saturation density and incompressibility modulus of nuclear matter are increased by using most of the hyperon-nucleon interaction.The centroid energies of GMR of hypernuclei ??42Ca,??210Pb are enhanced about 0.5 MeV compared to the values of corresponding normal nuclei,for the enhancement,one part is from the mean field calculation because the deeply bound states become more bound,another part is from the residual interactions associated with hyperons.The calculated effective incompressibility modulus of finite hypernuclei are increased,which are mainly due to the increasing of centroid energies.Then we have systematically investigated the dipole,quadrupole,octupole responses of double-?hypernuclei ??18O,??42Ca,??82Zr,??122Sn,??210Pb.Same as in GMR,We find the strength distributions of multipole excitations are shifted to higher energy region,the amount of enhancement depends on the type of mutipole excitations.For light hypernuclei,the shift comes mainly from the changes of single-particle levels,however,for heavier hypernuclei,it is the hyperon's residual interactions which make the response functions shifted upwards to high energy,the effects from mean field calculations are very small.The changes of transition densities in hypernuclei are different for each multipole response.In the dipole responses of finite hypernuclei,we find that a Pygmy resonance located in the low energy region appears,which is similar to the soft dipole motion in neutron-rich or proton-rich nuclei,the weakly bound valence neutrons oscillate against the core nucleus,here it is the hyperons who move against the core nucleus.On the other hand,the Pygmy and giant dipole resonances in proton-rich nuclei 17,18Ne have been investigated in a fully self-consistent Skyrme HF+BCS plus QRPA approach.In addition to the giant dipole resonances,pygmy dipole resonances are found to be located in the energy region below 10MeV in both 17,18Ne.The strength and transition density show that the low-lying states are typical PDR states.However,analyzing the QRPA amplitudes of proton and neutron 2 quasiparticle(2qp)configurations for a given low-lying state in 17,18Ne,we find that the PDR state is less collective,more like a single 2qp excitation.