The New Look pMSSM with Neutralino and Gravitino LSPs

TL;DR

This paper generates extensive pMSSM model sets with neutralino or gravitino LSPs, analyzing their cosmological constraints and LHC search coverage, providing valuable resources for future SUSY research.

Contribution

It introduces two large, viable pMSSM model sets with up to 4 TeV sparticle masses, incorporating cosmological constraints and LHC search analyses, especially for neutralino and gravitino LSP scenarios.

Findings

Gravitino LSP models face strong Big Bang Nucleosynthesis constraints.

LHC at 8 TeV with 5-20 fb^{-1} can probe about half of the neutralino LSP model set.

Non-MET SUSY searches remain crucial for exploring the pMSSM parameter space.

Abstract

The pMSSM provides a broad perspective on SUSY phenomenology. In this paper we generate two new, very large, sets of pMSSM models with sparticle masses extending up to 4 TeV, where the lightest supersymmetric particle (LSP) is either a neutralino or gravitino. The existence of a gravitino LSP necessitates a detailed study of its cosmological effects and we find that Big Bang Nucleosynthesis places strong constraints on this scenario. Both sets are subjected to a global set of theoretical, observational and experimental constraints resulting in a sample of \sim 225k viable models for each LSP type. The characteristics of these two model sets are briefly compared. We confront the neutralino LSP model set with searches for SUSY at the 7 TeV LHC using both the missing (MET) and non-missing ET ATLAS analyses. In the MET case, we employ Monte Carlo estimates of the ratios of the SM backgrounds at 7 and 8 TeV to rescale the 7 TeV data-driven ATLAS backgrounds to 8 TeV. This allows us to determine the pMSSM parameter space coverage for this collision energy. We find that an integrated luminosity of \sim 5-20 fb^{-1} at 8 TeV would yield a substantial increase in this coverage compared to that at 7 TeV and can probe roughly half of the model set. If the pMSSM is not discovered during the 8 TeV run, then our model set will be essentially void of gluinos and lightest first and second generation squarks that are \lesssim 700-800 GeV, which is much less than the analogous mSUGRA bound. Finally, we demonstrate that non-MET SUSY searches continue to play an important role in exploring the pMSSM parameter space. These two pMSSM model sets can be used as the basis for investigations for years to come.