MSSM fits to the ATLAS 1 lepton excess

TL;DR

This paper explores the p19MSSM parameter space to fit a mild excess observed in ATLAS 1-lepton + jets + MET searches, identifying specific spectra that could explain the signal without conflicting with other LHC results.

Contribution

It provides the first detailed fit of the ATLAS 1-lepton excess within the p19MSSM framework, proposing specific spectra that accommodate the excess and remain consistent with other searches.

Findings

Identified spectra with stops and sbottoms around 700-800 GeV fitting the excess.

Found scenarios with heavier squarks (~1.1-1.2 TeV) from cascade decays that also fit the data.

Global chi-squared analysis favors the signal hypothesis over the Standard Model background.

Abstract

We use the framework of the p19MSSM to perform a fit to the mild excesses over the Standard Model background recently observed in three bins of the ATLAS 1-lepton + (b-)jets + MET search. We find a few types of spectra that can fit the emerging signal and at the same time are not excluded by other LHC searches. They can be grouped roughly in two categories. The first class is characterized by the presence of one stop or stop and sbottoms with mass in the ballpark of 700-800 GeV and a neutralino LSP of mass around 400 GeV, with or without the additional presence of an intermediate chargino. In the second type of scenarios the stop, lightest chargino, sbottom if present, and the neutralino are about or heavier than ~650 GeV and the signal originates from cascade decays of squarks of the 1st and 2nd generation, which should have a mass of 1.1-1.2 TeV. For the best-fit scenarios, we compare the global chi-squared with respect to several ATLAS and CMS searches with the corresponding chi-squared of the Standard Model expectation, showing that the putative signal is also favored globally with respect to the background only hypothesis. We point out that if the observed excess persists in the next round of data, it should be accompanied by associated significant excesses in all-hadronic final state searches.