Long-lived particles: theory and experimental probes

TL;DR

This paper reviews the theoretical background and experimental methods for detecting long-lived particles at the LHC and other experiments, highlighting their significance in exploring physics beyond the Standard Model.

Contribution

It provides a comprehensive overview of LLP phenomenology, detection techniques, and the broader experimental landscape, including astrophysical and cosmological probes.

Findings

LLPs are common in the Standard Model and beyond.

Various experimental methods exist for LLP detection.

LLP searches complement other physics investigations.

Abstract

Long-lived particles (LLPs) are particles that are stable or that live long enough for their decays to be experimentally distinguishable in time or position from their production point. We provide an overview of the phenomenology and experimental signatures of LLPs, focusing on LLPs at the Large Hadron Collider (LHC). We explain what determines a particle's lifetime and we show that LLPs are ubiquitous both within the Standard Model and beyond. We survey the methods used to experimentally detect and characterize particles at collider-based experiments, and discuss how searches for LLPs present both experimental challenges and exciting new possibilities for detection. Finally, we situate LHC searches for LLPs within the broader experimental landscape with a brief overview of searches for LLPs at lower-energy experiments and a discussion of astrophysical and cosmological probes offering complementary insight into the physics of LLPs beyond the Standard Model.