Search for the direct production of charginos and neutralinos in $\sqrt{s}$ = 13 TeV $pp$ collisions with the ATLAS detector

TL;DR

This paper reports a search for charginos and neutralinos in proton-proton collisions at 13 TeV using the ATLAS detector, setting new exclusion limits on their masses in various supersymmetric scenarios.

Contribution

The study provides the first limits on chargino and neutralino production with tau final states at 13 TeV, extending previous searches and exploring different mass-splitting scenarios.

Findings

Chargino masses up to 630 GeV are excluded at 95% CL.

Neutralino and chargino masses up to 760 GeV are excluded.

No significant deviation from the Standard Model was observed.

Abstract

A search for the direct production of charginos and neutralinos in final states with at least two hadronically decaying tau leptons is presented. The analysis uses a dataset of $pp$ collisions corresponding to an integrated luminosity of 36.1 fb$^{-1}$, recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. No significant deviation from the Standard Model background expectation is observed. Limits are derived in scenarios of $\tilde{\chi}_{1}^{+}\tilde{\chi}_{1}^{-}$ pair production and of $\tilde{\chi}_{1}^{\pm}\tilde{\chi}_{2}^{0}$ and $\tilde{\chi}_{1}^{+}\tilde{\chi}_{1}^{-}$ production in simplified models where the neutralinos and charginos decay solely via intermediate left-handed staus and tau sneutrinos, and the mass of the $\tilde{\tau}_{\mathrm L}$ state is set to be halfway between the masses of the $\tilde{\chi}_{1}^{\pm}$ and the $\tilde{\chi}_{1}^{0}$. Chargino masses up to 630 GeV are excluded at 95% confidence level in the scenario of direct production of $\tilde{\chi}_{1}^{+}\tilde{\chi}_{1}^{-}$ for a massless $\tilde{\chi}_{1}^{0}$. Common $\tilde{\chi}_{1}^{\pm}$, $\tilde{\chi}_{2}^{0}$ masses up to 760 GeV are excluded in the case of production of $\tilde{\chi}_{1}^{\pm}\tilde{\chi}_{2}^{0}$ and $\tilde{\chi}_{1}^{+}\tilde{\chi}_{1}^{-}$ assuming a massless $\tilde{\chi}_{1}^{0}$. Exclusion limits for additional benchmark scenarios with large and small mass-splitting between the $\tilde{\chi}_{1}^{\pm}$ and the $\tilde{\chi}_{1}^{0}$ are also studied by varying the $\tilde{\tau}_{\mathrm L}$ mass between the masses of the $\tilde{\chi}_{1}^{\pm}$ and the $\tilde{\chi}_{1}^{0}$.