Efficient identification of boosted semileptonic top quarks at the LHC

By Keith R. Rehermann, B. Tweedie. 2010

232 citations recorded by the source corpus.

Top quarks produced in multi-TeV processes will have large Lorentz boosts, and their decay products will be highly collimated. In semileptonic decay modes, this often leads to the merging of the b-jet and the hard lepton according to standard event reconstructions, which can complicate new physics searches. Here we explore ways of efficiently recovering this signal in the muon channel at the LHC. We perform a particle-level study of events with muons produced inside of boosted tops, as well as in generic QCD jets and from W-strahlung off of hard quarks. We characterize the discriminating power of cuts previously explored in the literature, as well two new ones. We find a particularly powerful isolation variable which can potentially reject light QCD jets with hard embedded muons at the 103 level while retaining 80∼90% of the tops. This can also be fruitfully combined with other cuts for O(1) greater discrimination. For W-strahlung, a simple pT-scaled maximum ΔR cut performs comparably to a highly idealized top-mass reconstruction, rejecting an O(1) fraction of the background with percent-scale loss of signal. Using these results, we suggest a set of well-motivated baseline cuts for any physics analysis involving semileptonic top quarks at TeV-scale momenta, using neither b-tagging nor missing energy as discriminators. We demonstrate the utility of our cuts in searching for resonances in the $ t\bar{t} $ invariant mass spectrum. For example, our results suggest that 100 fb−1 of data from a 14 TeV LHC could be used to discover a warped KK gluon up to 4.5 TeV or higher.

Subfields: Artificial Intelligence, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0ac481ac20b4536ccd53a1fc4f16a6baf56f862d

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Citations in the corpus

Search for supersymmetry in multijet events with missing transverse momentum in proton-proton collisions at 13 TeV (2017, background): “The decrease in cone size with increasing lepton pT accounts for the increased collimation of the decay products from the lepton’s parent particle as the Lorentz boost of the parent particle increases [36].”
Jet substructure at the Large Hadron Collider (2018, methodology): “In ATLAS [186, 322], the lepton isolation is achieved by a variable isolation cone that changes as a function of the transverse momentum [323].”
Search for additional heavy neutral Higgs and gauge bosons in the ditau final state produced in 36 fb−1 of pp collisions at s=13$$ \sqrt{s}=13 $$ TeV with the ATLAS detector (2018, background): “3 and shrinking with increasing pT of the muon [81].”
Search for additional heavy neutral Higgs and gauge bosons in the ditau final state produced in 36 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector (2017, background): “3 and shrinking with increasing pT of the muon [81].”
Search for electroweak production of charginos and neutralinos in multilepton final states in proton-proton collisions at s=13$$ \sqrt{s}=13 $$ TeV (2017, methodology): “Loosely isolated leptons are required to have Imini 0.4.”
Search for supersymmetry in proton-proton collisions at 13 TeV in final states with jets and missing transverse momentum (2019, background): “The decrease in cone size with increasing lepton pT accounts for the increased collimation of the decay products from the lepton’s parent particle as the Lorentz boost of the parent particle increases [47].”
Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set at $\sqrt{s}=13$ TeV (2020, background): “3), labelled as p varcone30 T , where the latter is optimised for topologies where jets or other leptons are expected in close proximity to an energetic muon [34].”