Tau reconstruction at CMS with a focus on high $ p_{T} $ taus

Soham Bhattacharya

doi:10.21468/scipostphysproc.1.050

Abstract

We present the algorithm and performance of tau reconstruction at the CMS experiment, while highlighting a dedicated reconstruction algorithm that uses calorimeter hits instead of tracks to reconstruct taus with high transverse momentum. Describing the standard Hadrons-Plus-Strips (HPS) algorithm and its dependence on track reconstruction and shower modelling, we present the calorimetric tau (calo-tau) reconstruction that uses minimal track information for high p_{T}pT taus. The pros and cons of these algorithms are discussed along with their performance and potential uses. It is found that the calo-tau algorithm outperforms the HPS algorithm in the high efficiency region. This study is work in progress, and is an attempt to tune the reconstruction for high p_{T}pT taus. The calo-tau algorithm is not yet an official tau reconstruction algorithm for CMS.

Highlights

Searches involving high momenentum τ leptons have gained prominence in proton-proton collision at the LHC, in particular in the context of Beyond Standard Model physics
A calorimeter based tau reconstruction algorithm is more robust against possible mismodellings in Monte-Carlo simulations, and can serve as a crosscheck of whether potential high pT τh signals are lost in data
In the previous section we saw that that HPS algorithm relies heavily on track resolution, track momentum measurement, and electron, photon, and charged hadron reconstruction

Summary

Introduction

Searches involving high momenentum τ leptons have gained prominence in proton-proton collision at the LHC, in particular in the context of Beyond Standard Model physics (like heavy resonances decaying to taus). QCD jets are expected to have higher activity (tracks, calorimeter deposits) in an annular region around the signal cone compared to τh jets in which most of the energy is carried by the charged hadron and the electrons/photons in the signal cone. In the previous section we saw that that HPS algorithm relies heavily on track resolution, track momentum measurement, and electron, photon, and charged hadron reconstruction. The algorithm has been constructed in way such that its dependence on track momentum measurement in minimized, and unlike the HPS-tau algorithm, electron/photon/charged hadron reconstruction plays no role here. Figure 2: jet → τh misidentification probability versus the τh identification efficiency for the different isolation-based and MVA-based HPS-tau working points. The product ρAeff is the contribution from pileup to the ECAL energy deposits

CMS Simulation Preliminary

Comparison between τchalo and τHh PS performances

Conclusion