Search for top squarks in final states with many light-flavor jets and 0, 1, or 2 charged leptons in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for top squarks in proton-proton collisions at 13 TeV, using a novel machine learning background estimation method, setting new exclusion limits on top squark masses in RPV and stealth SUSY models.

Contribution

Introduces a new machine learning technique for background estimation in top squark searches with multiple light-flavor jets and leptons at the LHC.

Findings

Excluded top squark masses below 700 GeV for RPV SUSY.

Excluded top squark masses below 930 GeV for stealth SUSY.

Set upper limits on top squark pair production cross sections.

Abstract

Several new physics models including versions of supersymmetry (SUSY) characterized by $R$-parity violation (RPV) or with additional hidden sectors predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for top squarks decaying to two top quarks and six additional light-flavor quarks or gluons are reported. The search employs a novel machine learning method for background estimation from control samples in data using decorrelated discriminators. The search is performed using events with 0, 1, or 2 electrons or muons in conjunction with at least six jets. No requirement is placed on the magnitude of the missing transverse momentum. The result is based on a sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV corresponding to 138 fb$^{-1}$ of integrated luminosity collected with the CMS detector at the LHC in 2016$-$2018. The data are used to determine upper limits on the top squark pair production cross section in the frameworks of RPV and stealth SUSY. Models with top squark masses less than 700 (930) GeV are excluded at 95% confidence level for RPV (stealth) SUSY scenarios.