Alternative signatures of the quintuplet fermions at the LHC and future linear colliders

TL;DR

This paper explores unique collider signatures of heavy quintuplet fermions in extended Standard Model scenarios, proposing alternative search strategies at the LHC and future linear colliders, with potential for discovery within specific mass ranges.

Contribution

It introduces a scenario where quintuplet fermions are heavier than scalars, leading to non-standard decay signatures and alternative detection methods at colliders.

Findings

Doubly charged fermions can be discovered at the LHC for masses up to 980 GeV.

Singly charged fermions may be detectable at future linear colliders for masses up to 700 GeV.

Proposed strategies improve prospects for discovering exotic fermions beyond standard collider limits.

Abstract

Large fermionic multiplets appear in different extensions of the Standard Model (SM), which are essential to predict small neutrino masses, relic abundance of the dark matter (DM) and the measured value of muon anomalous magnetic moment (muon (g-2)). Models containing quintuplet of fermions ($\Sigma$), along with other scalar multiplets, can address recent anomalies in the flavor sector while satisfying the constraints from the electroweak physics. In standard scenarios, the exotic fermions couple with the SM particles directly and there exists a strong limit on their masses from collider experiments such as the Large Hadron Collider (LHC). In this paper, we choose a particular scenario where the quintuplet fermions are heavier than the scalars, which is naturally motivated from the muon (g-2) data. A unique nature of these models is that they predict non-standard signatures at the colliders as the quintuplet fermions decay via the scalars once produced at the colliders. We study these non-standard interactions and provide alternative search strategies for these exotic fermions at the LHC and future linear colliders (such as $e^+e^-$ colliders). We also discuss their exclusion and discovery limits. For the doubly charged quintuplet fermion ($\Sigma^{\pm\pm}$), discovery is possible with 5$\sigma$ significance at integrated luminosity of 3000 fb$^{-1}$ at 14 TeV LHC if $M_\Sigma\leq 980$ GeV. For the singly charged quintuplet fermion ($\Sigma^\pm$), the discovery is challenging at LHC but there might be a possibility of 5 $\sigma$ discovery with 1000 fb$^{-1}$ luminosity at $e^+e^-$ collider for $M_\Sigma\leq 700$ GeV.