Probing lepton flavour (universality) violation at NA62 and future kaon experiments

TL;DR

This paper explores how rare kaon decay experiments like NA62 can test new physics explanations for lepton flavour universality violations observed in B-meson decays, by relating low-energy constants to Wilson coefficients.

Contribution

It establishes a theoretical framework connecting kaon decay constants with B-physics anomalies within minimal flavour violation, guiding future experimental tests.

Findings

Relation between kaon decay constants and B-physics Wilson coefficients

Assessment of NA62's potential to probe lepton flavour violation

Required sensitivity improvements for future kaon experiments

Abstract

Recent results from the LHC's first run have revealed intriguing departures from lepton flavour universality in the semi-leptonic decays of $B$-mesons. We discuss the complementary role that rare kaon decays can provide in testing new physics explanations of these flavour anomalies. In the framework of minimal flavour violation, we relate the chiral low-energy constants involved in $K\to\pi\ell\ell'$ and $K\to\ell\ell'$ ($\ell = \mu \mbox{ or } e$) with the new physics Wilson coefficients of the $b\to s$ effective Hamiltonian. We comment on the determination of these low-energy constants at NA62 and future kaon experiments, as well as the required improvements in sensitivity necessary to test the $B$-physics anomalies in the kaon sector.