Accessing the core of naturalness, nearly degenerate higgsinos, at the LHC

TL;DR

This paper proposes a novel method to detect nearly degenerate higgsinos at the LHC by exploiting muon collinearity, achieving significant sensitivity even with small mass-splittings and high luminosity.

Contribution

It introduces a new analysis technique based on muon collinearity to identify degenerate higgsinos at the LHC, improving detection prospects in challenging scenarios.

Findings

Achieves ~2.9 sigma significance at 3000 fb$^{-1}$ for 124-120 GeV higgsinos.

Demonstrates good sensitivity for smaller mass-splittings with lighter higgsinos.

Provides a feasible search strategy for nearly degenerate higgsinos at the LHC.

Abstract

The presence of two light higgsinos nearly degenerate in mass is one of the important characteristics of suspersymmetric models meeting the naturalness criteria. Probing such higgsinos at the LHC is very challenging, in particular when the mass-splitting between them is less than 5 GeV. In this study, we analyze such a degenerate higgsino scenario by exploiting the high collinearity between the two muons which originate from the decay of the heavier higgsino into the lighter one and which are accompanied by a high-$p_T$ QCD jet. Using our method, we can achieve a statistical significance $\sim 2.9\,\sigma$ as well as a $S/B \sim 17\%$ with an integrated luminosity of 3000 fb$^{-1}$ at the 14 TeV LHC, for the pair production of higgsinos with masses 124 GeV and 120 GeV. A good sensitivity can be achieved even for a smaller mass-splitting when the higgsinos are lighter.