Exploring $\widetilde{R}_2$ Leptoquarks and Majorana Neutrinos via same-sign dimuons at the HL-LHC

TL;DR

This paper investigates the potential of the HL-LHC to detect scalar leptoquarks coupled with Majorana neutrinos through same-sign dimuon signatures, highlighting new search strategies beyond conventional methods.

Contribution

It introduces a comprehensive analysis of sLQ production modes at the HL-LHC, emphasizing the importance of both pair and single production in probing Majorana RHNs.

Findings

Pair production dominates at TeV scales.

Single production becomes significant at multi-TeV masses.

HL-LHC can explore parameter space beyond current constraints.

Abstract

We study the phenomenology of scalar leptoquark (sLQ) $\widetilde{R}_2$ coupled to right-handed neutrinos (RHNs) at the High-Luminosity Large Hadron Collider (HL-LHC), focusing on signatures that depart from those targeted by conventional sLQ searches at the LHC. If sLQ is heavier than the RHN, for $\mathcal{O}(1)$ Yukawa, the decay of sLQ to RHN and jet can dominate, leading to distinctive final states that are only weakly constrained by existing analysis. We consider the same sign dimuon and multi-jet signature. This is particularly a unique and clean lepton-number violating signature, benefiting from low Standard Model backgrounds and directly sensitive to the Majorana nature of the RHN. A comprehensive analysis is performed by combining the sLQ pair and single production mechanisms at $\sqrt{s}=14~\text{TeV}$, allowing us to assess the sensitivity reach of HL-LHC over a wide range of sLQ masses and Yukawa couplings. We demonstrate that pair production dominates the sensitivity at the TeV scale, while single production becomes increasingly important for multi-TeV sLQ masses, enabling the HL-LHC to probe regions of parameter space beyond the reach of current direct and indirect constraints. Our results highlight the strong complementarity between production modes and emphasize the unique capability of the HL-LHC to test sLQ scenarios involving RHNs. The framework presented here provides a well-motivated target for future experimental searches and offers a pathway toward simultaneously probing sLQ dynamics and parameter space of a Majorana RHN.