Reconstruction and identification of τ lepton decays to hadrons and ν_τat CMS

Abstract

This paper describes the algorithms used by the CMS experiment to reconstruct and identify τ → hadrons + ν τ decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb −1 . The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.The information available from all CMS subdetectors is employed in the particle-flow (PF) algorithm [38][39][40][41] to identify and reconstruct individual particles in the event, namely muons, electrons, photons, and charged and neutral hadrons. These particles are used to reconstruct jets, τ h candidates, and the vector imbalance in transverse momentum in the event, referred to as p miss T , as well as to quantify the isolation of leptons.Electrons are reconstructed by matching tracks in the inner detector with energy depositions 6 4 Event reconstruction A The CMS Collaboration

Search for electroweak production of charginos and neutralinos in WH events in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV

“…In order to reduce these backgrounds, we search for a second electron or muon with p T > 5 GeV and looser identification and isolation requirements, and reject events where such a lepton at higher values of lepton transverse momentum. We also reject events with reconstructed hadronically decaying tau leptons with p T > 20 GeV [52], or isolated tracks with p T > 10 GeV and opposite electric charge relative to the selected lepton. For this purpose, a track is considered isolated if p sum T /p T < 0.1 and p sum T < 6 GeV, where p sum T here is constructed with charged PF candidates compatible with the primary vertex, the cone radius is ∆R = 0.3, and p T is the transverse momentum of the track.…”

Search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\text {V} $$ s = 13 Te

“…Both are required to satisfy isolation requirements that limit the total energy of tracks and calorimeter clusters measured in conical regions about them. Hadronically decaying τ leptons, τ had , are reconstructed using the hadron-plus-strips algorithm [49], which uses charged hadron and neutral electromagnetic objects to reconstruct intermediate resonances into which the τ lepton decays. The τ had candidates with p T > 18 GeV and |η| < 2.3 are considered [47,49,50].…”

“…Hadronically decaying τ leptons, τ had , are reconstructed using the hadron-plus-strips algorithm [49], which uses charged hadron and neutral electromagnetic objects to reconstruct intermediate resonances into which the τ lepton decays. The τ had candidates with p T > 18 GeV and |η| < 2.3 are considered [47,49,50]. Photon candidates, identified by means of requirements on the ECAL energy distribution and its distance to the closest track, must have p T > 15 GeV and |η| < 2.5.…”

Naturalness confronts nature: searches for supersymmetry with the CMS detector in pp collisions at √s = 8 and $13$ TeV

“…We additionally reconstruct and identify hadronically decaying τ leptons (τ h ) to further enhance the all-hadronic purity of the zero-lepton event categories, using the hadron-plus-strips algorithm [225], which identifies τ decay modes with one charged hadron and up to two neutral pions, or three charged hadrons. The τ h candidate is required to have p T > 20 GeV, and the isolation, defined as the p T sum of other nearby PF candidates, must be below a certain threshold.…”

“…The τ h candidate is required to have p T > 20 GeV, and the isolation, defined as the p T sum of other nearby PF candidates, must be below a certain threshold. The loose cutoff-based selection [225] is used and results in an efficiency of about 50% for successfully reconstructed τ h decays.…”