# Constraints on new physics from $$K \rightarrow \pi \nu {\bar{\nu }}$$

The European Physical Journal C, Jun 2018

We study generic effects of new physics on the rare decay modes $$K_L \rightarrow \pi ^0 \nu {\bar{\nu }}$$ and $$K^+ \rightarrow \pi ^+ \nu {\bar{\nu }}$$. We discuss several cases: left-handed neutrino couplings; right handed neutrino couplings; neutrino lepton flavour violating (LFV) interactions; and $$\Delta I =3/2$$ 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 $$K_L \rightarrow \pi ^0 \nu {\bar{\nu }}$$ 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 $$\Delta I =3/2$$ 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.

This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1140%2Fepjc%2Fs10052-018-5964-0.pdf

Xiao-Gang He, German Valencia, Keith Wong. Constraints on new physics from $$K \rightarrow \pi \nu {\bar{\nu }}$$, The European Physical Journal C, 2018, 472, DOI: 10.1140/epjc/s10052-018-5964-0