Tau trigger, reconstruction and identification at CMS

Abstract

The importance of tau leptons in new physics searches at the LHC led the CMS collaboration to design a specific algorithm, the Hadron Plus Strip (HPS) algorithm, for the reconstruction and identification of taus decaying hadronically (${\tau }_{\mathrm{had}}$). The HPS algorithm makes use of a particle description of the event to identify hadronic decay modes of τ leptons through the reconstruction of intermediate resonances. It also provides discriminators against potentially large backgrounds from quarks, gluons and light leptons (electrons and muons). Moreover, thanks to the particle event reconstruction avalaible in CMS, a fast online hadronic tau reconstruction can be performed allowing the development of efficient tau trigger selections which allow to perform a broad range of physics analysis. This report describes the ${\tau }_{\mathrm{had}}$ reconstruction and identification of the HPS algorithm and its performances, studied in simulated $Z\to \tau \tau$ events and in samples of proton-proton collision data collected during 2011 and 2012 data-taking at $\sqrt{s}=7\mathrm{TeV}\text{and}8\mathrm{TeV}$, respectively. Finally, the performance of the tau trigger selections is presented.