The End of the CMSSM Coannihilation Strip is Nigh

TL;DR

Recent analyses suggest the CMSSM's coannihilation strip is nearing its end, with current LHC data already excluding some scenarios and future detection prospects discussed.

Contribution

This paper provides the first comprehensive analysis of the CMSSM coannihilation strip's viability in light of recent experimental constraints.

Findings

CMSSM coannihilation points with small mass differences are excluded by LHC searches.

Most favored points have long-lived staus detectable as heavy charged particles.

Detection strategies include time-of-flight and anomalous ionization measurements.

Abstract

A recent global fit to the CMSSM incorporating current constraints on supersymmetry, including missing transverse energy searches at the LHC, BR(B_s to mu+ mu-) and the direct XENON100 search for dark matter, favours points towards the end of the stau-neutralino (stau_1- chi) coannihilation strip with relatively large m_1/2 and 10 < tan beta < 40 and points in the H/A rapid-annihilation funnel with tan beta ~ 50. The coannihilation points typically have m_stau_1-m_chi < 5 GeV, and a significant fraction, including the most-favoured point, has m_stau_1-m_chi < m_tau. In such a case, the stau_1 lifetime would be so long that the stau_1 would be detectable as a long-lived massive charged particle that may decay inside or outside the apparatus. We show that CMSSM scenarios close to the tip of the coannihilation strip for tan beta < 40 are already excluded by LHC searches for massive charged particles, and discuss the prospects for their detection in the CMS and ATLAS detectors via time-of-flight measurements, anomalous heavy ionization or decays into one or more soft charged particles.