Abstract

This document summarises recent ATLAS results for searches for third generation squarks using 36.1 [Formula: see text] of LHC proton-proton collision data collected at [Formula: see text] TeV. Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. Supersymmetry can naturally solve the Standard Model hierarchy problem by preventing a large fine-tuning in the Higgs sector: a typical natural SUSY spectrum contains light third generation squarks (stops and sbottoms). Both R-Parity conserving and R-Parity violating scenarios are considered. The searches involve final states including jets, missing transverse momentum, electrons or muons. Simplified models predicting pair production of third generation squarks have been excluded at 95% CL up to about one TeV in the most favourable scenarios.

Highlights

  • Supersymmetry (SUSY)[1] provides an extension of the Standard Model (SM) by introducing partners of the known bosons and fermions differing by half-unit of spin

  • In the framework of R-paritya conserving models, SUSY particles are produced in pairs and the lightest supersymmetric particle (LSP) is stable and a possible candidate for dark matter[2,3]

  • The background estimates in the SRs are validated by extrapolating the results of the likelihood fit in the Control regions (CRs) to dedicated validation regions (VRs), which are designed to be orthogonal to both the signal and the control regions and are usually kinematically closer to the SR than the CR

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Summary

Introduction

Supersymmetry (SUSY)[1] provides an extension of the Standard Model (SM) by introducing partners of the known bosons and fermions differing by half-unit of spin. Introducing non-zero R-parity violating (RPV) couplings into supersymmetric models provides additional phenomenology: the most relevant fact is that the LSP is unstable and decays to SM particles. Naturalness considerations[4,5] suggest that aR-parity is a discrete multiplicative symmetry defined as R = 13B+L+2s, where B is the baryon number, L the lepton number and s the spin. This is an Open Access article published by World Scientific Publishing Company. F. Meloni the supersymmetric partners of the third-generation SM quarks are the lightest coloured SUSY particles. Unknown sparticle masses are free parameters and each specific decay is assumed to occur with a 100% branching ratio (BR)

Summary of the Search Selections
Final states with no leptons
Final states with one lepton
Final states with two leptons
Final states with Higgs- or Z-bosons
Interpretation of the Results
Conclusions
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