Abstract
Abstract:
A search is presented for the pair production of heavy vector-like quarks, TT¯ or BB¯, that decay
into final states with jets and no reconstructed leptons. Jets in the final state are classified
using a deep neural network as arising from hadronically decaying W /Z bosons, Higgs bosons, top
quarks, or background. The analysis uses data from the ATLAS experiment
corresponding to 36.1 fb−1 of proton–proton collisions with a center-of-mass energy of √s =
13 TeV delivered by the Large Hadron Collider in 2015 and 2016. No significant deviation from the
Standard Model expectation is observed. Results are interpreted assuming the vector- like quarks
decay into a Standard Model boson and a third-generation-quark, T → W b, Ht, Zt or B → Wt, Hb, Z b,
for a variety of branching ratios. At 95% confidence level, the observed (expected) lower limit on
the vector-like B-quark mass for a weak-isospin doublet (B, Y ) is 950 (890) GeV, and the lower
limits on the masses for the pure decays B → Hb and T → Ht, where these results are strongest, are
1010 (970) GeV and 1010 (1010) GeV, respectively.