Search for a feebly interacting particle $X$ in the decay $K^{+}\to {\pi }^{+}X$

Abstract

A search for the $K^{+}\to {\pi }^{+}X$ decay, where $X$ is a long-lived feebly interacting particle, is performed through an interpretation of the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ analysis of data collected in 2017 by the NA62 experiment at CERN. Two ranges of $X$ masses, $0$-$110\text{MeV}/c^2$ and $154$-$260\text{MeV}/c^2$, and lifetimes above $100\text{ps}$ are considered. The limits set on the branching ratio, $\text{BR}(K^{+}\to {\pi }^{+}X)$, are competitive with previously reported searches in the first mass range, and improve on current limits in the second mass range by more than an order of magnitude.

14 pages, 6 figures, accepted for publication by JHEP

Cited by in corpus (2)

• Leptonic Meson Decays into Invisible ALP
• LHC experiments for long-lived particles of the dark sector