Search for Resonances Decaying into Top Quark Pairs Using Fully Hadronic Decays in $pp$ Collisions with ATLAS at $\sqrt{s}$ = 7 $TEV$

A search for new particles that decay into top-quark pairs producing two massive jets with high transverse momentum is presented. Data collected with the ATLAS detector at the Large Hadron Collider during the proton-proton collision run at $\sqrt{s}=7\,\textrm{TeV}$ in 2011 is analysed. The substructure-based HEPTopTagger technique is used to separate top-quark jets from those arising from light quarks or gluons. The performance of this method is evaluated using a statistically independent sample. Top-quark candidates are also required to have a bottom-quark decay associated with them. The backgrounds are estimated using data-driven techniques. No significant deviation between data and the sum of Standard Model background processes, such as $t\overline{t}$ production and multijet production, is observed in the di-top invariant mass spectrum $m_{t\overline{t}}$. Therefore limits on the production cross section times branching fractions of certain models of $Z^{\prime}$ boson and a Kaluza-Klein gluon resonances are set. The production of $Z^{\prime}$ bosons with masses between 0.70 and 1.00~TeV as well as 1.28 and 1.32~TeV and Kaluza-Klein gluons with masses between 0.70 and 1.48~TeV is excluded at $95\%$ C.L.