Frederic Noël
(ITP, AEC, Uni Bern)
Lepton-flavor-violating decays of light pseudoscalars, , are stringently suppressed in the Standard Model up to tiny contributions from neutrino oscillations, so that their observation would be a clear indication for physics beyond the Standard Model.
However, in effective field theory such decays proceed via axial-vector, pseudoscalar, or gluonic operators, which are, at the same time, probed in spin-dependent conversion in nuclei.
We derive master formulae that connect both processes in a model-independent way in terms of Wilson coefficients, which in the case of conversion in nuclei requires input for the nuclear matrix elements including the charge density to account for the bound-state physics, and study the implications of current μ → e limits in titanium for the P → μe decays. We find that these indirect limits surpass direct ones by many orders of magnitude.
based on: Phys.Rev.Lett. 130 (2023) 13, 131902
Martin Hoferichter
(University of Bern)
Javier Menéndez
(University of Barcelona)
Frederic Noël
(ITP, AEC, Uni Bern)
