Search for $W' \rightarrow tb \rightarrow qqbb$ Decays in pp Collisions at $\sqrt{s}$ = 8 TeV with the ATLAS Detector

TL;DR

This paper searches for high-mass $W'$ bosons decaying to top and bottom quarks in 8 TeV proton-proton collisions, using advanced jet substructure techniques to identify top quarks, and sets upper limits on production cross sections and couplings.

Contribution

It introduces novel jet substructure methods for identifying high-momentum top quarks in $W'$ boson searches at the LHC.

Findings

No significant excess over Standard Model background.

Upper limits on $W'$ production cross section range from 0.10 to 0.33 pb.

Constraints on $W'$-boson couplings are established.

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 $\sqrt{s} = 8$ TeV and corresponds to 20.3 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 $1.5 - 3.0$ 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 $0.16$ pb to $0.33$ pb for left-handed $W'$ bosons, and ranging from $0.10$ pb to $0.21$ 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.