Search for the direct production of charginos and neutralinos in final states with tau leptons in $\sqrt {s} =$ 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 p$-$p 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 $\sqrt{s} =$ 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 $\tilde\chi^\pm_1 \tilde\chi^0_2$ and $\tilde\chi^+_1 \tilde\chi^-_1$ production. 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 $\tilde\chi^0_1$. Common $\tilde\chi^\pm_1$, $\tilde\chi^0_2$ masses up to 760 GeV are excluded at 95% confidence level in the case of production of $\tilde\chi^\pm_1 \tilde\chi^0_2$ and $\tilde\chi^+_1 \tilde\chi^-_1$ assuming a massless $\tilde\chi^0_1$.