Reinterpretation of searches for long-lived particles from meson decays

TL;DR

This paper introduces a simple reinterpretation method for long-lived particles produced from meson decays, enabling quick bounds estimation without extensive simulations, applicable to various models like heavy neutral leptons and axion-like particles.

Contribution

The authors present a novel, simulation-free method for reinterpreting experimental bounds on LLPs from meson decays, applicable across different theoretical frameworks.

Findings

Successfully reproduces existing bounds from CHARM and Belle experiments.

Extends reinterpretation to general EFT frameworks and axion-like particles.

Provides a quick and accessible approach for future LLP searches.

Abstract

Many models beyond the Standard Model predict light and feebly interacting particles that are often long-lived. These long-lived particles (LLPs) in many cases can be produced from meson decays. In this work, we propose a simple and quick reinterpretation method for models predicting LLPs produced from meson decays. With the method, we are not required to run Monte-Carlo simulation, implement detector geometries and efficiencies, or apply experimental cuts in an event analysis, as typically done in recasting and reinterpretation works. The main ingredients our method requires are only the theoretical input, allowing for computation of the production and decay rates of the LLPs. There are two conditions for the method to work: firstly, the LLPs in the models considered should be produced from a set of mesons with similar mass and lifetime (or the same meson) and second, the LLPs should, in general, have a lab-frame decay length much larger than the distance between the interaction point and the detector. As an example, we use this method to reinterpret exclusion bounds on heavy neutral leptons (HNLs) in the minimal ``3+1'' scenario, into those for HNLs in the general effective-field-theory framework as well as for axion-like particles. We are able to reproduce existing results, and obtain new bounds via reinterpretation of past experimental results, in particular, from CHARM and Belle.