A search for a new massive charged gauge boson, W', is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton-proton collisions at a centre-of-mass energy of SQUARE ROOT s = 13TeV, and corresponds to an integrated luminosity of 139 fb-1.
The reconstructed tb invariant mass is used to search for a W' boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a W' boson with purely right-handed or left-handed chirality in a mass range of 0.5-6TeV.
Different values for the coupling of the W' boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the s-channel. No significant deviation from the background prediction is observed.
The results are expressed as upper limits on the W' RIGHTWARDS ARROW tb production cross-section times branching ratio as a function of the W'-boson mass and in the plane of the coupling vs the W'-boson mass.