at a rate of one out of tau decays?
Department of Physics, Indiana University, Bloomington, IN, 47408, USA
2 Center for Exploration of Energy and Matter, Indiana University, Bloomington, IN, 47408, USA
3 Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany
4 Theoretische Physik I, Universität Siegen, 57068, Siegen, Germany
5 Theory Center, Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606, USA
* e-mail: email@example.com
Accepted: 19 May 2020
Published online: 5 June 2020
We present in a full analytic form the partial widths for the lepton flavour violating decays and , with , mediated by neutrino oscillations in the one-loop diagrams. Compared to the first result by Petcov (Sov J Nucl Phys 25:340, 1977), obtained in the zero momentum limit , we retain full dependence on , the momenta and masses of external particles, and we determine the branching ratios in the physical limit . We show that the claim presented in Pham (Eur Phys J C8:513, 1999) that the branching ratios could be as large as , as a consequence of keeping the dependence, is flawed. We find rates of order , even smaller than those obtained in the zero momentum limit, as the latter prediction contains an unphysical logarithmic enhancement.
© The Author(s), 2020