Abstract
A search for a massive W' gauge boson decaying to a top quark and a bottom quark is performed with the ATLAS detector in pp collisions at the LHC. The dataset was taken at a centre-of-mass energy of sqrt{s} = 8{mathrm { TeV}} and corresponds to 20.3,text{ fb }^{-1} of integrated luminosity. This analysis is done in the hadronic decay mode of the top quark, where novel jet substructure techniques are used to identify jets from high-momentum top quarks. This allows for a search for high-mass W' bosons in the range 1.5–3.0 {mathrm { TeV}}. b-tagging is used to identify jets originating from b-quarks. The data are consistent with Standard Model background-only expectations, and upper limits at 95 % confidence level are set on the W'rightarrow tb cross section times branching ratio ranging from 0.16,mathrm {pb} to 0.33,mathrm {pb} for left-handed W' bosons, and ranging from 0.10,mathrm {pb} to 0.21,mathrm {pb} for W' bosons with purely right-handed couplings. Upper limits at 95 % confidence level are set on the W'-boson coupling to tb as a function of the W' mass using an effective field theory approach, which is independent of details of particular models predicting a W' boson.
Highlights
The search for a W boson decaying to a top quark and a bquark (W → tb)1 explores models potentially inaccessible to W → ν searches
This allows for good sensitivity at high W masses. 95 % Confidence Level (CL) exclusion limits are presented on the W -boson coupling as a function of the W mass in an effective model
It is calculated by reclustering the constituents of the large-R jet using the kT algorithm, where the reclustering procedure is stopped at the last merging step
Summary
The search for a W boson decaying to a top quark and a bquark (W → tb) explores models potentially inaccessible to W → ν searches. This document describes the first search for the W → tb process in the fully hadronic final state of the top-quark decay. For high W masses, the final state signature consists of one high-momentum b-quark and another b-quark close to the two light-quarks from the W -boson decay. The distinct signature of high-momentum top quarks is exploited to isolate the signal from the copious hadronic multijet background making use of novel jet substructure techniques to identify boosted hadronically decaying top quarks. This allows for good sensitivity at high W masses. This allows for good sensitivity at high W masses. 95 % CL exclusion limits are presented on the W -boson coupling as a function of the W mass in an effective model
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