# Nuclear Physics Theory

Lead Research Organisation:
University of York

Department Name: Physics

### Abstract

To establish a Chair in Nuclear physics theory at the University of York with the overall goal of enhancing the provision of nuclear theory within the UK.

### Planned Impact

It is expected that this appointment will both complement the exisiting nuclear theory group work as well as enhance the provision of nuclear physics theory in the UK.

### Publications

Baczyk P
(2015)

*Strong-interaction Isospin-symmetry Breaking Within the Density Functional Theory*in Acta Physica Polonica B Proceedings Supplement
Baczyk P
(2018)

*Isospin-symmetry breaking in masses of N ? Z nuclei*in Physics Letters B
Baczyk P
(2017)

*Mirror and Triplet Displacement Energies Within Nuclear DFT: Numerical Stability*in Acta Physica Polonica B
Baczyk P
(2019)

*Isobaric multiplet mass equation within nuclear density functional theory*in Journal of Physics G: Nuclear and Particle Physics
Becker P
(2018)

*Skyrme N2LO Pseudo-potential for Calculations of Properties of Atomic Nuclei*in Acta Physica Polonica B
Becker P
(2015)

*Tools for incorporating a D-wave contribution in Skyrme energy density functionals*in Journal of Physics G: Nuclear and Particle Physics
Becker P
(2017)

*Solution of Hartree-Fock-Bogoliubov equations and fitting procedure using the N2LO Skyrme pseudopotential in spherical symmetry*in Physical Review C
Bennaceur K
(2017)

*Nonlocal energy density functionals for pairing and beyond-mean-field calculations*in Journal of Physics G: Nuclear and Particle Physics
Chamel N
(2015)

*Brussels--Montreal Nuclear Energy Density Functionals, from Atomic Masses to Neutron Stars*in Acta Physica Polonica B
Davesne D
(2018)

*Two-body contributions to the effective mass in nuclear effective interactions*in Physical Review CDescription | We extended the nuclear Density Functional Theory (DFT) by including proton-neutron mixing and contact isospin-symmetry-breaking (ISB) terms up to next-to-leading order (NLO). Within this formalism, we performed systematic study of the nuclear mirror and triple displacement energies, or equivalently of the Isobaric Multiplet Mass Equation (IMME) coefficients. By comparing results with those obtained within the existing Green Function Monte Carlo (GFMC) calculations, we addressed the fundamental question of the physical origin of the ISB effects. This we achieved by analysing separate contributions to IMME coefficients coming from the electromagnetic and nuclear ISB terms. We showed that the ISB DFT and GFMC results agree reasonably well, and that they describe experimental data with a comparable quality. Since the separate electromagnetic and nuclear ISB contributions also agree, we concluded that the beyond-mean-field electromagnetic effects may not play a dominant role in describing the ISB effects in finite nuclei. Elucidating the appropriate microscopic degrees of freedom within neutron stars remains an open question, which affects nuclear physics, particle physics, and astrophysics. The recent discovery of the first non-trivial dibaryon, the d?(2380), provides a new candidate for an exotic degree of freedom in the nuclear equation of state at high matter densities. Using a relativistic mean-field approach, we have performed the very first study of the equation of state of dense nuclear matter including this new particle. The calculations have shown that that the d?(2380) would appear at densities around three times normal nuclear matter saturation density and comprise around 20% of the matter in the centre of heavy stars with higher fractions possible in the higher densities of merger processes. The d?(2380) would also reduce the maximum star mass by around 15% and have significant influence on the fractional proton/neutron composition. New possibilities for neutron star cooling mechanisms arising from the d?(2380) have been also predicted. We showed that the measured intrinsic octupole moments of 220Rn, 224Ra, and 226Ra constrain the intrinsic Schiff moments of 225Ra, 221Rn, 223Rn, 223Fr, 225Ra, and 229Pa. The result is a dramatically reduced uncertainty in intrinsic Schiff moments. Direct measurements of octupole moments in odd nuclei will reduce the uncertainty even more. The only significant source of nuclear-physics error in the laboratory Schiff moments will then be the intrinsic matrix elements of the time-reversal noninvariant interaction produced by CP-violating fundamental physics. Those matrix elements are also correlated with octupole moments, but with a larger systematic uncertainty. We proposed to use two-body regularized finite-range pseudopotential to generate nuclear energy density functional (EDF) in both particle-hole and particle-particle channels, which makes it free from self-interaction and self-pairing, and also free from singularities when used beyond mean field. We derived a sequence of pseudopotentials regularized up to next-to-leading order (NLO) and next-to-next-to-leading order (N$^2$LO), which fairly well describe infinite-nuclear-matter properties and finite open-shell paired and/or deformed nuclei. We proposed a simple and manageable method that allows for deriving coupling constants of model energy density functionals (EDFs) directly from ab initio calculations performed for finite fermion systems. A proof-of-principle application allows for linking properties of finite nuclei, determined by using the nuclear nonlocal Gogny functional, to the coupling constants of the quasilocal Skyrme functional. The method does not rely on properties of infinite fermion systems but on the ab initio calculations in finite systems. It also allows for quantifying merits of different model EDFs in describing the ab initio results. |

Exploitation Route | The new proposed methodology may find applications in numerous fields of many-body physics |

Sectors | Chemicals,Digital/Communication/Information Technologies (including Software),Education |

Description | FiDiPro |

Organisation | University of Jyvaskyla |

Department | Department of Physics |

Country | Finland |

Sector | Academic/University |

PI Contribution | Long-term scientific collaboration and publications |

Collaborator Contribution | Long-term scientific collaboration and publications |

Impact | 10.1103/PhysRevC.97.024306, 10.1088/1361-6471/aa691e, 10.1088/1361-6471/aa5fd7, 10.1016/j.cpc.2017.03.007 |

Start Year | 2007 |

Description | Lyon Claud Bernard |

Organisation | University of Lyon |

Country | France |

Sector | Academic/University |

PI Contribution | Long-term scientific collaboration and publications |

Collaborator Contribution | Long-term scientific collaboration and publications |

Impact | 10.1088/1361-6471/aa691e, 10.1088/1361-6471/aa5fd7 |

Description | MSU Nazarewicz |

Organisation | Michigan State University |

Department | Department ofÂ PhysicsÂ And Astronomy |

Country | United States |

Sector | Academic/University |

PI Contribution | Long-term collaboration and publications |

Collaborator Contribution | Long-term collaboration and publications |

Impact | 10.5506/APhysPolB.46.575 |

Description | Warsaw IFT |

Organisation | University of Warsaw |

Country | Poland |

Sector | Academic/University |

PI Contribution | Long-term scientific collaboration and publications |

Collaborator Contribution | Long-term scientific collaboration and publications |

Impact | 10.1103/PhysRevC.94.024306, 10.1016/j.cpc.2017.03.007, 10.5506/APhysPolB.48.259, 10.1016/j.physletb.2017.12.068 |