Written by R.L. Kelly （LBNL）. The most commonly used SU（3） isoscalar factors, corresponding to the singlet, octet, and deeuplet content of 8 8 and 10 8, are shown at the right. The notation uses particle nam...Written by R.L. Kelly （LBNL）. The most commonly used SU（3） isoscalar factors, corresponding to the singlet, octet, and deeuplet content of 8 8 and 10 8, are shown at the right. The notation uses particle names to identify the coefficients, so that the pattern of relative couplings may be seen at a glance. We illustrate the use of the coefficients below.展开更多
The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, wh...The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, whose Hamiltonian is diagonalized in the basis U(24) ?(U(6) ? S U(3) ? S O(3))■(U(4) ? S US(2)■ S UT(2)) in the L = 0 configuration subspace. Besides the pairing interaction, it is observed that the quadurpole-quadurpole and particlehole interactions also play a significant role in determining the relative positions of low-lying excited 0^+ and 1^+ levels and their energy gaps, which can result in the ground state first-order quantum phase transition from J = 0 to J = 1.The strengths of the isovector and isoscalar pairing interactions in these even-even nuclei are estimated with respect to the energy gap and the total contribution to the binding energy. Most importantly, it is shown that although the mechanism of the particle-hole contribution to the binding energy is different, it is indirectly related to the Wigner term in the binding energy.展开更多
本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位...本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位旋标量对力对于恢复SU(4)对称性从而重现实验上42Ca的低能量超级GT态至关重要。同位旋标量对力会使自旋反转的跃迁组分混合进入低能量GT态,从而增强低能量GT态的集体性,极大地增加其跃迁强度。同时,由于同位旋标量对力具有吸引性质,会减小低能量GT态的激发能。对于SD跃迁,同位旋标量对力对其激发能和跃迁强度的影响均不明显。展开更多
The effects of the tensor force on the and decay nuclear matrix elements(NMEs)of,,,and are studied using the Hartree-Fock-Bogoliubov(HFB)plus proton-neutron quasi-particle random phase approximation(pnQRPA)model based...The effects of the tensor force on the and decay nuclear matrix elements(NMEs)of,,,and are studied using the Hartree-Fock-Bogoliubov(HFB)plus proton-neutron quasi-particle random phase approximation(pnQRPA)model based on the Skyrme energy density functional.We include the full spectra of intermediate states with up to the energy cutoff E=60 MeV,which is sufficient for convergence of NME calculations.The isovector(IV)pairing and tensor interactions are considered in both HFB and QRPA calculations,while the isoscalar(IS)pairing interaction is included only in QRPA calculations.We found that the tensor force shifts Gamow-Teller(GT)transition strengths substantially to low-energy regions and enhances the decay NME.The inclusion of tensor force enhances the NME by approximately 13%for and and 30%for and,for a fixed IS pairing strength.We found that the intermediate 2-state makes an important contribution to the NME,which is slightly enhanced by the inclusion of the tensor force.We also found that the contribution of the state makes important differences through the inclusion of the tensor force,which enhances the contribution largely.However when the IS pairing strength is increased,the contributions from 1+states are rapidly reduced to be very small,resulting in even negative contributions.Thus,tensor and IS pairing effects cancel each other,making the net effect on the NME relatively small.Due to this cancellation,if the IS pairing strength is optimized separately for cases with and without the tensor interaction to reproduce the experimental NME,the consequent NME with the tensor interaction is close to that without the tensor interaction within a 10%difference.展开更多
A short overview over the ABC phenomenon is given,which is known since 50 years without any satisfactory explanation.On the basis of new exclusive and kinematically complete data obtained with the WASA detector at COS...A short overview over the ABC phenomenon is given,which is known since 50 years without any satisfactory explanation.On the basis of new exclusive and kinematically complete data obtained with the WASA detector at COSY we show that this phenomenon is linked with a resonant energy dependence in the total cross section of isoscalar double-pionic fusion processes.This resonance structure is connected with the baryon-baryon system,in particular with the pn and ΔΔ systems,however,has a mass,which is 90 MeV below the nominal ΔΔ threshold and a width of only 70 MeV,i.e.,five times smaller than expected from a conventional t-channel ΔΔ scenario.展开更多
文摘Written by R.L. Kelly （LBNL）. The most commonly used SU（3） isoscalar factors, corresponding to the singlet, octet, and deeuplet content of 8 8 and 10 8, are shown at the right. The notation uses particle names to identify the coefficients, so that the pattern of relative couplings may be seen at a glance. We illustrate the use of the coefficients below.
基金Supported by the National Natural Science Foundation of China(11675071 and 11375080)the U.S.National Science Foundation(OIA-1738287 and ACI-1713690)+2 种基金U.S.Department of Energy(DE-SC0005248)the Southeastern Universities Research Association,the China-U.S.Theory Institute for Physics with Exotic Nuclei(CUSTIPEN)(DE-SC0009971)the LSU-LNNU joint research program(9961)
文摘The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, whose Hamiltonian is diagonalized in the basis U(24) ?(U(6) ? S U(3) ? S O(3))■(U(4) ? S US(2)■ S UT(2)) in the L = 0 configuration subspace. Besides the pairing interaction, it is observed that the quadurpole-quadurpole and particlehole interactions also play a significant role in determining the relative positions of low-lying excited 0^+ and 1^+ levels and their energy gaps, which can result in the ground state first-order quantum phase transition from J = 0 to J = 1.The strengths of the isovector and isoscalar pairing interactions in these even-even nuclei are estimated with respect to the energy gap and the total contribution to the binding energy. Most importantly, it is shown that although the mechanism of the particle-hole contribution to the binding energy is different, it is indirectly related to the Wigner term in the binding energy.
文摘本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位旋标量对力对于恢复SU(4)对称性从而重现实验上42Ca的低能量超级GT态至关重要。同位旋标量对力会使自旋反转的跃迁组分混合进入低能量GT态,从而增强低能量GT态的集体性,极大地增加其跃迁强度。同时,由于同位旋标量对力具有吸引性质,会减小低能量GT态的激发能。对于SD跃迁,同位旋标量对力对其激发能和跃迁强度的影响均不明显。
基金Supported by the National Natural Science Foundation of China(11575120,11822504,12075104)National Key Research and Development(R&D)programe of China(2021YFA1601500)+2 种基金Science Specialty Program of Sichuan University(2020SCUNL210)the support from Chinese Academy of Sciences for the project of Young Scientists in Basic Research(YSBR-099)"From 0 to 1 innovative"program.This work was partially supported by JSPS KAKENHI(JP19K03858)。
文摘The effects of the tensor force on the and decay nuclear matrix elements(NMEs)of,,,and are studied using the Hartree-Fock-Bogoliubov(HFB)plus proton-neutron quasi-particle random phase approximation(pnQRPA)model based on the Skyrme energy density functional.We include the full spectra of intermediate states with up to the energy cutoff E=60 MeV,which is sufficient for convergence of NME calculations.The isovector(IV)pairing and tensor interactions are considered in both HFB and QRPA calculations,while the isoscalar(IS)pairing interaction is included only in QRPA calculations.We found that the tensor force shifts Gamow-Teller(GT)transition strengths substantially to low-energy regions and enhances the decay NME.The inclusion of tensor force enhances the NME by approximately 13%for and and 30%for and,for a fixed IS pairing strength.We found that the intermediate 2-state makes an important contribution to the NME,which is slightly enhanced by the inclusion of the tensor force.We also found that the contribution of the state makes important differences through the inclusion of the tensor force,which enhances the contribution largely.However when the IS pairing strength is increased,the contributions from 1+states are rapidly reduced to be very small,resulting in even negative contributions.Thus,tensor and IS pairing effects cancel each other,making the net effect on the NME relatively small.Due to this cancellation,if the IS pairing strength is optimized separately for cases with and without the tensor interaction to reproduce the experimental NME,the consequent NME with the tensor interaction is close to that without the tensor interaction within a 10%difference.
基金Supported by BMBF (06TU261,06TU9193)Forschungszentrum Jülich (COSY-FFE)DFG (Europ.Graduiertenkolleg 683)
文摘A short overview over the ABC phenomenon is given,which is known since 50 years without any satisfactory explanation.On the basis of new exclusive and kinematically complete data obtained with the WASA detector at COSY we show that this phenomenon is linked with a resonant energy dependence in the total cross section of isoscalar double-pionic fusion processes.This resonance structure is connected with the baryon-baryon system,in particular with the pn and ΔΔ systems,however,has a mass,which is 90 MeV below the nominal ΔΔ threshold and a width of only 70 MeV,i.e.,five times smaller than expected from a conventional t-channel ΔΔ scenario.
