Boosted Jet Substructure Research Articles

Search for pair production of vector-like T and B quarks in single-lepton final states using boosted jet substructure in proton-proton collisions at sqrt{s}=13 TeV

A search for pair production of massive vector-like T and B quarks in proton-proton collisions at sqrt{s}=13 TeV is presented. The data set was collected in 2015 by the CMS experiment at the LHC and corresponds to an integrated luminosity of up to 2.6 fb−1. The T and B quarks are assumed to decay through three possible channels into a heavy boson (either a W, Z or Higgs boson) and a third generation quark. This search is performed in final states with one charged lepton and several jets, exploiting techniques to identify W or Higgs bosons decaying hadronically with large transverse momenta. No excess over the predicted standard model background is observed. Upper limits at 95% confidence level on the T quark pair production cross section are set that exclude T quark masses below 860 GeV in the singlet, and below 830 GeV in the doublet branching fraction scenario. For other branching fraction combinations with ℬ(T → tH) + ℬ(T → bW) ≥ 0.4, lower limits on the T quark range from 790 to 940 GeV. Limits are also set on pair production of singlet vector-like B quarks, which can be excluded up to a mass of 730 GeV. The techniques showcased here for understanding highly-boosted final states are important as the sensitivity to new particles is extended to higher masses.

Top polarization and stop mixing from boosted jet substructure

Top polarization is an important probe of new physics that couples to the top sector, and which may be discovered at the 14 TeV LHC. Taking the example of the MSSM, we argue that top polarization measurements can put a constraint on the soft supersymmetry breaking parameter A t . In light of the recent discovery of a Higgs-like boson of mass ∼ 125 GeV, a large A t is a prediction of many supersymmetric models. To this end, we develop a detector level analysis methodology for extracting polarization information from hadronic tops using boosted jet substructure. We show that with 100 fb−1 of data, left and right 600 GeV stops can be distinguished to 4σ, and 800 GeV stops can be distinguished to 3σ.

Top Polarization from Boosted Jet Substructure

Top polarization is an important probe of new physics that couples to the top sector, and which may be discovered at the 14 TeV LHC. Taking the example of the MSSM, we develop a detector level analysis methodology for extracting polarization information from hadronic tops using boosted jet substructure. We show that with 100 fb-1 of data, left and right 600 GeV stops can be distinguished to 4,5σ, and 800 GeV stops can be distinguished to 3σ.