Searching for ALP Lepton Flavor Violation via ALP Decays at the LHC

TL;DR

This paper investigates the potential to detect lepton flavor violation mediated by axion-like particles at the LHC, focusing on ALP production and decay into electron-muon pairs, and presents improved sensitivity limits in the 5-1000 GeV mass range.

Contribution

It introduces a novel search strategy for ALP-induced lepton flavor violation at the LHC, emphasizing the decay channel into electron-muon pairs and providing enhanced sensitivity limits.

Findings

Significantly improved limits on ALP couplings in the 5-1000 GeV mass range.

Effective background suppression techniques for ALP detection.

Feasibility of observing LFV signals via ALP decays at the LHC.

Abstract

In the ALP model, lepton flavor violation (LFV) can arise from off-diagonal ALP-lepton couplings ($g_{a\ell_i\ell_j}$), which are absent in the Standard Model. We focus on ALP production via gluon fusion ($pp \to a$) at the Large Hadron Collider (LHC), which dominates the ALP mass range of 5-1000 GeV due to its high cross section and manageable backgrounds. We are interested in the decay of an axion into an electron and a muon, two oppositely charged leptons of different flavors. After background suppression, we obtain the sensitivity to ALP in this mass range, finding significantly improved limits for $5 < m_a < 1000$ GeV, where SM backgrounds are suppressed. Our research is complementary with relevant studies.