Session 3WFB: Nuclear Theory for New Physics II

Quantification of the electric dipole moment generated by elementary particle physics

The atomic, nuclear, and nucleon electric dipole moments (EDMs) have significant sensitivity to the CP violation of elementary particle physics [1], but its quantification has for long been obstructed by the nonperturbative physics of quantum chromodynamics. Quite recently, there were significant progresses in this subject, notably the resolution of the strong CP problem and the quantification of hadron level CP violation such as the contributions of the quark chromo-EDM and Weinberg operator (CP violating three-gluon interaction) to the CP-odd hadronic interactions. We are therefore almost attaining the quantification era of the CP violating hadronic interaction in the leading order of standard model effective field theory. In this talk, we summarize the current attempt to quantify the hadronic CP violation contribution to the EDM of nucleons, nuclei, and atoms.

[1] N. Yamanaka et al., Eur. Phys. J. A 53 (2017) 54.   

Shell-model studies of medium-heavy nuclei for the neutrinoless-double-beta-decay matrix element and the nuclear Schiff moment

Various search experiments have been performed for new physics beyond the standard model. In these experimental studies, theoretical nuclear structure physics plays an essential role. For example, the nuclear matrix element must be theoretically estimated for the neutrinoless double-beta decay experiments. In this talk, we discuss the neutrinoless-double-beta-decay matrix element of 150Nd and its relation to its nuclear structure, especially to the shape phase transition of the Nd and Sm isotopes, by the large-scale shell-model calculations. We also evaluated the nuclear Schiff moments of 129Xe and 199Hg for the experimental effort to find permanent electric dipole moments. We discuss the nuclear Schiff moment and its relation to the magnetic moment.   

Constraints on charged lepton flavor violation from muon-to-electron conversion in nuclei

Muon-to-electron conversion is one of our most sensitive probes of charged lepton flavor violation (CLFV). Depending on the underlying BSM mechanism, the next-generation experiments Mu2e at Fermilab and COMET at J-PARC may probe new physics at scales up to 10,000 TeV. Complementary physics information can be obtained by varying the nuclear target. If the process is mediated by exchange of a heavy scalar particle, it is possible to predict the expected CLFV branching ratio with a well-understood uncertainty, yielding rigorous constraints on the parameters of candidate UV models. Beyond this simplest coherent scenario, the most general CLFV interaction including spin- and velocity-dependent nuclear responses was recently constructed. We discuss this progress and the outstanding challenges towards leveraging the full power of Mu2e and COMET to probe BSM physics.