Beyond Cuts in Small Signal Scenarios - Enhanced Sneutrino Detectability Using Machine Learning

The absence of a signal of new particles at the Large Hadron Collider (LHC) may suggest that new physics is realized in a scenario that is hard to detect due to the absence or very large mass of new colored particles. Hence, this study focuses on setups with dominant electroweak production of color-neutral new particles and multi-lepton signals from their decays. The conventional approach to searches for new physics, also known as "cut-and-count analysis", is to apply a set of constraints on different kinematic variables (called "cuts" or "selection") that improve the signalto-background ratio. However, the scenarios we consider can be challenging for this standard approach due to the small production cross section and the similarity of signal and background features. For such problems, machine learning (ML) offers a promising alternative [1-6]. We investigate how much ML can increase the discovery reach, and whether machine learning models can be trained in such a way that they work in a large region of parameter space and not just for a single point. This is an important issue, in particular in new physics scenarios with many free parameters, as signal kinematics vary from point to point. As a concrete example, we consider a supersymmetry (SUSY) scenario with a gravitino lightest supersymmetric particle (LSP) whose mass is in the GeV range.