On the coverage of the pMSSM by simplified model results

TL;DR

This paper evaluates how well simplified model results from ATLAS and CMS cover the parameter space of the pMSSM, showing that about 60% of excluded points are captured, with potential improvements identified.

Contribution

It introduces the SModelS tool for automating the interpretation of simplified model results and compares its coverage to full simulation studies of the pMSSM.

Findings

Approximately 60% of ATLAS-excluded pMSSM points are also excluded by simplified models.

Considering missing simplified model topologies could improve coverage.

Asymmetric topologies, especially 3 jet + missing energy signatures, are crucial for coverage.

Abstract

ATLAS and CMS have been performing a large number of searches for physics beyond the Standard Model (BSM). In particular results of supersymmetry (SUSY) searches are typically interpreted in the context of simplified models. While mass limits obtained in this manner are highly model dependent, cross section upper limits (or efficiency maps) may be used to obtain constraints on generic BSM scenarios without any further event and detector simulation. This procedure has been automatised in the public tool SModelS, which first decomposes the generic scenario into its simplified model components which can then be tested directly against the experimental constraints in the SModelS database. We briefly introduce SModelS and then discuss how the coverage by simplified model results compares to what can be obtained in a full simulation study for the example of the 19 parameter phenomenological MSSM (pMSSM). Considering all parameter points that ATLAS has tested in a comprehensive study [1], we find that about 60 % of the points excluded by ATLAS can be excluded from simplified model constraints. This fraction could be improved by considering currently `missing' simplified model topologies. We show that in particular topologies with asymmetric branches are often important, while long cascade decays with more than one intermediate particle are less relevant. A particularly interesting asymmetric branch topology is a 3 jet + $E_T^{\mathrm{miss}}$ signature arising from gluino-squark production.