Abstract
We compute the electric dipole polarizability of Ca48 with an increased precision by including more correlations than in previous studies. Employing the coupled-cluster method we go beyond single and double excitations and include leading-order three-particle-three-hole (3p-3h) excitations for the ground state, excited states, and the similarity-transformed operator. We study electromagnetic sum rules, such as the bremsstrahlung sum rule m0 and the polarizability sum rule αD using interactions from chiral effective field theory. To gauge the quality of our coupled-cluster approximations we perform several benchmarks with the effective interaction hyperspherical harmonics approach in He4 and with self consistent Green's function in O16. We compute the dipole polarizability of Ca48 employing the chiral interaction N2LOsat [Ekström, Phys. Rev. C 91, 051301 (2015)PRVCAN0556-281310.1103/PhysRevC.91.051301] and the 1.8/2.0 (EM) [Hebeler, Phys. Rev. C 83, 031301 (2011)PRVCAN0556-281310.1103/PhysRevC.83.031301]. We find that the effect of 3p-3h excitations in the ground state is small for 1.8/2.0 (EM) but non-negligible for N2LOsat. The addition of these new correlations allows us to improve the precision of our Ca48 calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined αD from proton inelastic scattering in Ca48 [Birkhan, Phys. Rev. Lett. 118, 252501 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.252501]. For the computation of electromagnetic and polarizability sum rules, the inclusion of leading-order 3p-3h excitations in the ground state is important, while it is less so for the excited states and the similarity-transformed dipole operator.
| Original language | English |
|---|---|
| Article number | 014324 |
| Journal | Physical Review C |
| Volume | 98 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jul 23 2018 |
Funding
This work was supported in part by the Natural Sciences and Engineering Research Council (NSERC), by the National Research Council of Canada, by the Deutsche Forschungsgemeinschaft DFG through the Collaborative Research Center [The Low-Energy Frontier of the Standard Model (SFB 1044)], and through the Cluster of Excellence [Precision Physics, Fundamental Interactions and Structure of Matter (PRISMA)], by the Office of Nuclear Physics, U.S. Department of Energy under Grants No. DE-FG02-96ER40963 (University of Tennessee), No. DE-SC0008499 (SciDAC-3 NUCLEI), No. DE-SC0018223 (SciDAC-4 NUCLEI), and the Field Work Proposals ERKBP57 and ERKBP72 at Oak Ridge National Laboratory. Computer time was provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. This research used resources of the Oak Ridge Leadership Computing Facility located in the Oak Ridge National Laboratory (ORNL), supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, and computational resources of the National Center for Computational Sciences, the National Institute for Computational Sciences, and TRIUMF.