Signal optimization for a $W' \rightarrow t\bar{b}$ search in proton-proton collisions at 7~TeV with the ATLAS detector

Many theories beyond the Standard Model, e.g. extra-dimension model, technicolor theory and little higgs theory, predict the existence of $W'$ boson. Here, we present the search of $W'$ production in single top channel using the LHC pp collision data collected with the ATLAS detector at a center-of-mass energy of 7~TeV. The top quark decays via $t \rightarrow Wb$ with only the semileptonic decay channel being considered, thus $W' \rightarrow t\bar{b} \rightarrow l \nu b\bar{b}$. In this case, the $W'$ signal appears in the detector as two jets from b-quarks, a lepton and missing transverse energy from a neutrino. In order to distinguish this process from the background contribution that mainly consists of multijets, W+jets and top quark pair events, with smaller contributions from Z+jets, single top and diboson events, additional variables are applied to optimize the $W'$ signal. A fitting method using the invariant mass distribution of the final state particles has been used to set limits on the $W' \rightarrow t\bar{b}$ cross section times branching ratio as a function of the $W'$ mass.