Speaker
Description
A search for compressed supersymmetry in the stau-neutralino ($\tilde{\tau}\tilde{\chi}^{0}_{1}$) coannihilation region is presented. The search targets final states with exactly one low-energy (``soft'') hadronically-decaying $\tau$ lepton and large missing transverse momentum ($\vec{E}^{miss}_{T}$) due to the natural kinematic boost from a high transverse momentum jet from initial state radiation (ISR). The data sample corresponds to an integrated luminosity of 77.2 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = 13$ TeV collected with CMS detector at the CERN LHC in 2016 and 2017. The distribution of the transverse mass between the $\tau_{h}$ and the $\vec{E}^{miss}_{T}$ is found to be consistent with the standard model predictions. Upper limits are set on the cross section for chargino ($\tilde{\chi}^{\pm}_{1}$) and neutralino ($\tilde\chi^{0}_{2}$) production with an associated ISR jet. For a compressed mass spectrum scenario in which the mass difference between the $\tilde{\chi}^{0}_{1}$ and the $\tilde{\chi}^{\pm}_{1}$ is 50 GeV, an upper limit of 290 GeV is set on the mass of the $\tilde\chi^{\pm}_{1}$, which exceeds the sensitivity obtained by other $\tilde{\tau}$ searches to date. Finally, the results are also interpreted considering direct production of $\tilde{\tau}$ pairs with associated ISR jets.
