Exotic Lepton Searches via Bound State Production at the LHC

TL;DR

This paper introduces a new method to search for heavy, multi-charged leptons at the LHC by detecting their bound states in diphoton resonance channels, significantly improving existing mass bounds.

Contribution

It proposes a novel search strategy for multi-charged leptons via their bound states and demonstrates enhanced mass exclusion limits using current LHC data.

Findings

Excluded heavy lepton masses up to ~1.2 TeV at 8 TeV LHC data.

Projected exclusion of masses up to ~1.6 TeV at 13 TeV LHC data.

Enhanced limits by including photon fusion processes in searches.

Abstract

Heavy long-lived multi-charged leptons (MCLs) are predicted by various new physics models. These hypothetical MCLs can form bound states, due to their high electric charges and long life times. In this work, we propose a novel strategy of searching for MCLs through their bound state productions and decays. By utilizing LHC-8 TeV data in searching for resonances in the diphoton channel, we exclude the masses of isospin singlet heavy leptons with electric charge $|q|\geq 6$ (in units of electron charge) lower than $\sim$1.2 TeV, which are much stronger than the corresponding 8 TeV LHC bounds from analysing the high ionisation and the long time-of-flight of MCLs. By utilising the current 13 TeV LHC diphoton channel measurements the bound can further exclude MCL masses up to $\sim$1.6 TeV for $|q|\geq 6$. Also, we demonstrate that the conventional LHC limits from searching for MCLs produced via Drell-Yan processes can be enhanced by including the contribution of photon fusion processes.