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' → W- tW+ t → bbW+ W- W+ W- → l± νbbqqqqqq. 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 can be excluded at the 95% confidence level.
Highlights
This Letter presents a search for pair production of heavy down-type quarks decaying via b0 ! Wt in the lepton þ jets channel, as b0b"0 ! WÀtWþt" ! bb"WþWÀWþWÀ ! lÆbb"qq"qq"qq"
In addition to requiring exactly one lepton, large missing transverse momentum, and at least six jets, the invariant mass of nearby integrated jet pairs is luminosity used to of 1:04 identify high transverse fbÀ1 from pp collisions matopmffisffie1⁄4ntu7mTWeVbroescoonrsd.eIdnwdiatthatchoerAreTspLoAnSdidnegtetcotoarn, a heavy down-type quark with mass less than 480 GeV can be excluded at the 95% confidence level
A fourth generation of chiral quarks is a natural extension to the standard Model (SM)
Summary
This Letter presents a search for pair production of heavy down-type quarks decaying via b0 ! Wt in the lepton þ jets channel, as b0b"0 ! WÀtWþt" ! bb"WþWÀWþWÀ ! lÆbb"qq"qq"qq". The rate of top quark production predicted by the simulation is validated with data using an event sample with three, four, or five jets, where little or no b0 signal is expected. The W þ jets background is normalized using a datadriven method which fits templates from simulated events to a data sample dominated by W decays [18].
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