https://doi.org/10.1140/epjc/s10052-018-5964-0
Regular Article - Theoretical Physics
Constraints on new physics from 
1
Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
2
Physics Division, National Center for Theoretical Sciences, Hsinchu, 30013, Taiwan
3
Tsung-Dao Lee Institute, and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
4
School of Physics and Astronomy, Monash University, Melbourne, VIC, 3800, Australia
* e-mail: german.valencia@monash.edu
Received:
26
April
2018
Accepted:
31
May
2018
Published online:
9
June
2018
We study generic effects of new physics on the rare decay modes 
and 
. We discuss several cases: left-handed neutrino couplings; right handed neutrino couplings; neutrino lepton flavour violating (LFV) interactions; and 
interactions. The first of these cases has been studied before as it covers many new physics extensions of the standard model; the second one requires the existence of a new light (sterile) right-handed neutrino and its contribution to both branching ratios is always additive to the SM. The case of neutrino LFV couplings introduces a CP conserving contribution to which affects the rates in a similar manner as a right handed neutrino as neither one of these interferes with the standard model amplitudes. Finally, we consider new physics with interactions to go beyond the Grossman-Nir bound. We find that the rare kaon rates are only sensitive to new physics scales up to a few GeV for this scenario.
© The Author(s), 2018
