Machine Learning Electroweakino Production

TL;DR

This paper applies machine learning techniques to improve the detection of electroweakinos at the LHC, enhancing signal-background discrimination and sensitivity to new physics in challenging signatures.

Contribution

It introduces ML methods combining reconstructed and low-level data, demonstrating improved discrimination and sensitivity in electroweakino searches at the LHC.

Findings

ML improves S/√(S+B) by a factor of two over simple cuts

Lowering pT threshold to 1 GeV increases discrimination performance

Enhanced sensitivity to squark-electroweakino mass plane at Run-3 and HL-LHC

Abstract

The system of light electroweakinos and heavy squarks gives rise to one of the most challenging signatures to detect at the LHC. It consists of missing transverse energy recoiled against a few hadronic jets originating either from QCD radiation or squark decays. The analysis generally suffers from the large irreducible Z + jets $(Z \to \nu \bar \nu)$ background. In this study, we explore Machine Learning (ML) methods for efficient signal/background discrimination. Our best attempt uses both reconstructed (jets, missing transverse energy, etc.) and low-level (particle-flow) objects. We find that the discrimination performance improves as the pT threshold for soft particles is lowered from 10 GeV to 1 GeV, at the expense of larger systematic uncertainty. In many cases, the ML method provides a factor two enhancement in $S/\sqrt{(S + B)}$ from a simple kinematical selection. The sensitivity on the squark-elecroweakino mass plane is derived with this method, assuming the Run-3 and HL-LHC luminosities. Moreover, we investigate the relations between input features and the network's classification performance to reveal the physical information used in the background/signal discrimination process.