Displaced Supersymmetry

TL;DR

This paper explores how R-parity violation in supersymmetry can lead to long-lived particles causing displaced vertices, which evade many collider searches, thus relaxing superpartner mass constraints and suggesting new search strategies.

Contribution

It demonstrates that bilinear RPV allows for long-lived LSPs with displaced decays, significantly weakening existing superpartner mass bounds and motivating targeted collider searches.

Findings

Superpartner mass constraints can be as low as ~450 GeV for squarks.

LSP decay lengths of 1-1000 mm are viable and detectable.

Displaced vertices can hide Higgs decays from current searches.

Abstract

The apparent absence of light superpartners at the LHC strongly constrains the viability of the MSSM as a solution to the hierarchy problem. These constraints can be significantly alleviated by R-parity violation (RPV). Bilinear R-parity violation, with the single operator L H_u, does not require any special flavor structure and can be naturally embedded in a GUT while avoiding constraints from proton decay (unlike baryon-number-violating RPV). The LSP in this scenario can be naturally long-lived, giving rise to displaced vertices. Many collider searches, particularly those selecting b-jets or leptons, are insensitive to events with such detector-scale displaced decays owing to cuts on track quality and impact parameter. We demonstrate that for decay lengths in the window ~1-1000 mm, constraints on superpartner masses can be as low as ~450 GeV for squarks and ~40 GeV for LSPs. In some parts of parameter space light LSPs can dominate the Higgs decay width, hiding the Higgs from existing searches. This framework motivates collider searches for detector-scale displaced vertices. LHCb may be ideally suited to trigger on such events, while ATLAS and CMS may need to trigger on missing energy in the event.