Searches for hidden sectors using $K^+\to\pi^+X$ decays

TL;DR

This paper reports on the NA62 experiment's search for hidden sector particles through rare kaon decays, setting new limits on models involving dark photons, scalars, and axion-like particles.

Contribution

It provides the most stringent experimental limits to date on hidden-sector mediators from kaon decay processes.

Findings

Achieved world-leading limits on dark photon models.

Set new constraints on dark scalar and axion-like particles.

Enhanced understanding of potential hidden-sector interactions.

Abstract

Results from the study of the rare decays $K^+\to\pi^+\nu\bar{\nu}$, $K^{+}\rightarrow\pi^{+}\mu^{+}\mu^{-}$ and $K^{+}\rightarrow\pi^{+}\gamma\gamma$ at the NA62 experiment at CERN are interpreted in terms of improved limits for $\rm{B}(K^+\to\pi^+X)$ and coupling parameters of hidden-sector models, where $X$ is a mediator. World-leading limits are achieved for dark photon, dark scalar and axion-like particle models.