CP violation in neutral lepton transition dipole moment

• Published in: The journal of high energy physics Vol. 2020; no. 12; pp. 1 - 17
• Main Authors: Balaji, Shyam, Ramirez-Quezada, Maura, Zhou, Ye-Ling
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2020; Springer Nature B.V; SpringerOpen
• Subjects: Asymmetry; Classical and Quantum Gravitation; CP violation; Dipole moments; Elementary Particles; Flavor (particle physics); Form factors; High energy physics; Leptons; Matter & antimatter; Neutrino Physics; Neutrinos; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Regular Article - Theoretical Physics; Relativity Theory; String Theory; Neutrino Physics; CP violation
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP12(2020)090

A bstract The CP violation in the neutrino transition electromagnetic dipole moment is discussed in the context of the Standard Model with an arbitrary number of right-handed singlet neutrinos. A full one-loop calculation of the neutrino electromagnetic form factors is performed in the Feynman gauge. A non-zero CP asymmetry is generated by a required threshold condition for the neutrino masses along with non-vanishing CP violating phases in the lepton flavour mixing matrix. We follow the paradiagm of CP violation in neutrino oscillations to parametrise the flavour mixing contribution into a series of Jarlskog-like parameters. This formalism is then applied to a minimal seesaw model with two heavy right-handed neutrinos denoted N 1 and N 2 . We observe that the CP asymmetries for decays into light neutrinos N → νγ are extremely suppressed, maximally around 10 − 17 . However the CP asymmetry for N 2 → N 1 γ can reach of order unity. Even if the Dirac CP phase δ is the only source of CP violation, a large CP asymmetry around 10 − 5 –10 − 3 is comfortably achieved.