Search for down-type fourth generation quarks with the ATLAS detector in events with one lepton and hadronically decaying W bosons

TL;DR

This paper reports a search for heavy down-type fourth-generation quarks decaying into W bosons and b quarks, using ATLAS data, and sets a mass exclusion limit below 480 GeV.

Contribution

It introduces a novel search strategy for down-type fourth-generation quarks in the lepton + jets channel with specific event selection criteria.

Findings

Excluded down-type quark masses below 480 GeV at 95% CL.

Implemented a method to identify high transverse momentum W bosons.

Analyzed 1.04 fb^-1 of proton-proton collision data at 7 TeV.

Abstract

This Letter presents a search for pair production of heavy down-type quarks decaying via b'->Wt in the lepton + jets channel, as b'b'->WtWt->bbWWWW->lvbbqqqqqq. In addition to requiring exactly one lepton, large missing transverse momentum and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum W bosons. In data corresponding to an integrated luminosity of 1.04 fb^-1 from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector, a heavy down-type quark with mass less than 480 GeV is excluded at the 95% confidence level.