Feasibility Study of Lepton Number Violation in Rare $B$ and $K$ Meson Decays

TL;DR

This paper investigates lepton-number-violating interactions at dimension seven within the Standard Model effective field theory, focusing on their effects on rare meson decays, neutrino masses, and implications for baryon asymmetry.

Contribution

It identifies conditions for observing lepton-number violation in rare meson decays and demonstrates the compatibility of these interactions with neutrino mass generation.

Findings

Lepton-number-violating interactions can affect $B$ and $K$ meson decay rates.

These interactions can generate neutrino masses at two-loop level.

The scenario remains consistent with the presence of the Weinberg operator.

Abstract

We study lepton-number-violating interactions at dimension seven in the Standard Model effective field theory that contribute to the meson decays $B \to K \nu \nu$ and $K \to \pi \nu \nu$. Such interactions could washout the baryon asymmetry of the Universe and also contribute to the neutrinoless double beta decay, even though the interactions involve a change in down-type quark flavors. We clarify conditions under which excesses in meson decay rates over the Standard Model predictions can be successfully observed. We also show that, although these interactions contribute to neutrino masses at the two-loop level, the Weinberg operator can be introduced consistently without spoiling the scenario.