Search for the Direct Production of Charginos and Neutralinos in Final States with Tau Leptons in √s =13 TeV pp Collisions with the ATLAS Detector

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 expected Standard Model background is observed. Limits are derived in scenarios of χ̅₁⁺ χ̅₁⁻ pair production and of χ̅₁ ± χ̅₂⁰ and χ̅₁⁺ χ̅₁⁻ production in simplified models where the neutralinos and charginos decay solely via intermediate left-handed staus and tau sneutrinos, and the mass of the τ˜_L state is set to be halfway between the masses of the and the χ̅₁± and the χ̅₁⁰. Chargino masses up to 630 GeV are excluded at 95% confidence level in the scenario of direct production of χ̅₁⁺ χ̅₁⁻ for a massless χ̅₁⁰. Common χ̅₁± and χ̅₂⁰ masses up to 760 GeV are excluded in the case of production of χ̅₁± χ̅₂⁰ and χ̅₁⁺ χ̅₁⁻ assuming a massless χ̅₁⁰. Exclusion limits for additional benchmark scenarios with large and small mass-splitting between the χ̅₁± χ̅₂ and the χ̅₁⁺ χ̅₁⁻ are also studied by varying the τ˜_L mass between the masses of the χ̅₁± and the χ̅₁⁰.