# Compressed Stop Searches with Two Leptons and Two b-jets

## TL;DR

This paper extends compressed stop searches to dileptonic decays, introducing new kinematic variables based on the $R_M$ ratio interval, enhancing the ability to distinguish signals from backgrounds in challenging scenarios.

## Contribution

It generalizes the $R_M$ variable method to dileptonic stop decays, providing new discriminating variables that improve search sensitivity in compressed spectra scenarios.

## Key findings

- New variables derived from $R_M$ interval effectively discriminate signals.
- Dileptonic stop searches become more competitive with the new method.
- Expanded parameter space coverage for stop searches in compressed spectra.

## Abstract

In top squark (stop) searches with a compressed spectrum, it is very helpful to consider the stop production recoiling against a hard jet from the initial state radiation to obtain a significant amount of missing transverse energy. In particular, the kinematic variable $R_M$ which measures the ratio of the lightest neutralino mass and the stop mass proved to be crucial in separating the signals from the backgrounds in both the all-hadronic decay and the semileptonic decay of the stops. Here we generalize the search method to the dileptonic stop decays. In this case, due to the two missing neutrinos, there are not enough kinematic constraint equations to solve for the $R_M$ variable exactly, but only render an allowed interval consistent with the event. However, we show that the minimum and the maximum values of this allowed interval still provide useful variables in discriminating signals from the backgrounds. Although in the traditional stop decay to a top quark and the lightest neutralino, the dileptonic mode is not as competitive due to its small branching ratio, it becomes the main search mode if the stops decay through the charginos and sleptons with a compressed spectrum. We show that with the new variables, the dileptonic search of the stop can cover regions of the parameter space which have not been constrained before.