Preprint/Internal Report DESY-2013-00615

A search for $\it{t\bar{t}}$ resonances in lepton plus jets events with ATLAS using 14 $fb^{-1}$ of proton-proton collisions at $\sqrt{s} = 8$ TeV

(Corresponding author)

2013

Report No.: ATLAS-CONF-2013-052;

Abstract: A search for new particles that decay into top quark pairs (t¯t) is performed with theATLAS experiment at the LHC using an integrated luminosity of 14 fb􀀀1 of proton-protoncollision data collected at center-of-mass energyps = 8 TeV. The lepton plus jets final stateis used, where the top-pair decays as t¯t ! W+bW􀀀¯b with oneW boson decaying leptonicallyand the other hadronically. The t¯t system is reconstructed using both a conventional resolvedjet analysis and a large-radius jet substructure analysis. The t¯t invariant mass spectrum issearched for local excesses deviating from the Standard Model prediction. No evidence fora t¯t resonance is found and 95% CL limits on the production rate are determined for massivestates in two benchmark models. The upper limits on the cross section times branching ratioof a narrow Z′ boson decaying to top pairs range from 5.3 pb for a resonance mass of 0.5 TeVto 0.08 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z′ boson with a mass below1.8 TeV is excluded. Upper limits are set on the cross section times branching ratio for abroad color-octet resonance with 􀀀=m = 15.3% decaying to t¯t. These range from 9.6 pb fora mass of 0.5 TeV to 0.152 pb for a mass of 2.5 TeV. A Kaluza-Klein excitation of the gluonin a Randall–Sundrum model is excluded for masses below 2.0 TeV.

Note: 16 May 2013;First Large Hadron Collider Physics Conference, Barcelona, Spain, 13 - 18 May 2013; Copyright 2013 CERN for the benefit of the ATLAS Collaboration. Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.

Contributing Institute(s):
1. LHC/ATLAS Experiment (ATLAS)
Research Program(s):
1. Experiments at LHC (ATLAS) (POF2-512) (POF2-512)
Experiment(s):
1. LHC: ATLAS

Appears in the scientific report 2013
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