Deep learning for the R-parity violating supersymmetry searches at the LHC

TL;DR

This paper develops a deep neural network approach, specifically a CNN using jet images, to improve the detection of neutralino jets in R-parity violating supersymmetry searches at the LHC, outperforming traditional methods.

Contribution

It introduces a CNN-based jet tagging method that enhances neutralino jet identification and applies it to recast ATLAS data, improving gluino mass exclusion limits.

Findings

CNN outperforms N-subjettiness in jet tagging efficiency

Combining CNN output with jet mass improves detection across neutralino masses

Exclusion limits on gluino mass increased by approximately 200 GeV

Abstract

Supersymmetry with hadronic R-parity violation in which the lightest neutralino decays into three quarks is still weakly constrained. This work aims to further improve the current search for this scenario by the boosted decision tree method with additional information from jet substructure. In particular, we find a deep neural network turns out to perform well in characterizing the neutralino jet substructure. We first construct a Convolutional Neutral Network (CNN) which is capable of tagging the neutralino jet in any signal process by using the idea of jet image. When applied to pure jet samples, such a CNN outperforms the N-subjettiness variable by a factor of a few in tagging efficiency. Moreover, we find the method, which combines the CNN output and jet invariant mass, can perform better and is applicable to a wider range of neutralino mass than the CNN alone. Finally, the ATLAS search for the signal of gluino pair production with subsequent decay $\tilde{g} \to q q \tilde{\chi}^0_1 (\to q q q)$ is recasted as an application. In contrast to the pure sample, the heavy contamination among jets in this complex final state renders the discriminating powers of the CNN and N-subjettiness similar. By analyzing the jets substructure in events which pass the ATLAS cuts with our CNN method, the exclusion limit on gluino mass can be pushed up by $\sim200$ GeV for neutralino mass $\sim 100$ GeV.