Signal region combination with full and simplified likelihoods in MadAnalysis 5

TL;DR

This paper introduces methods for combining signal regions in MadAnalysis 5 using full and simplified likelihoods, enhancing the robustness and physics reach of reinterpretation studies in particle physics analyses.

Contribution

It presents new implementations of signal region combination in MadAnalysis 5 via pyhf interface and simplified likelihood methods using covariance matrices, improving analysis sensitivity.

Findings

Demonstrated increased physics reach through comparison with official mass limits.

Validated methods with analyses from ATLAS and CMS collaborations.

Case study shows improved sensitivity in MSSM scenarios.

Abstract

The statistical combination of disjoint signal regions in reinterpretation studies uses more of the data of an analysis and gives more robust results than the single signal region approach. We present the implementation and usage of signal region combination in MadAnalysis 5 through two methods: an interface to the pyhf package making use of statistical models in JSON-serialised format provided by the ATLAS collaboration, and a simplified likelihood calculation making use of covariance matrices provided by the CMS collaboration. The gain in physics reach is demonstrated 1.) by comparison with official mass limits for 4 ATLAS and 5 CMS analyses from the Public Analysis Database of MadAnalysis 5 for which signal region combination is currently available, and 2.) by a case study for an MSSM scenario in which both stops and sbottoms can be produced and have a variety of decays into charginos and neutralinos.