TY - JOUR AU - ATLAS Collaboration (Aad, G. et al AU - Alvarez Piqueras, D. AU - Cabrera Urban, S. AU - Castillo Gimenez, V. AU - Costa, M. J. AU - Fernandez Martinez, P. AU - Ferrer, A. AU - Fiorini, L. AU - Fuster, J. AU - Garcia, C. AU - Garcia Navarro, J. E. AU - Gonzalez de la Hoz, S. AU - Hernandez Jimenez, Y. AU - Higon-Rodriguez, E. AU - Irles Quiles, A. AU - Jimenez Pena, J. AU - Kaci, M. AU - King, M. AU - Lacasta, C. AU - Lacuesta, V. R. AU - Marti-Garcia, S. AU - Mitsou, V. A. AU - Moles-Valls, R. AU - Oliver Garcia, E. AU - Pedraza Lopez, S. AU - Perez Garcia-Estañ, M. T. AU - Romero Adam, E. AU - Ros, E. AU - Salt, J. AU - Sanchez Martinez, V. AU - Soldevila, U. AU - Sanchez, J. AU - Torro Pastor, E. AU - Valero, A. AU - Valladolid Gallego, E. AU - Valls Ferrer, J. A. AU - Vos, M. PY - 2015 DA - 2015// TI - A search for t(t)over-bar resonances using lepton-plus-jets events in proton-proton collisions at root s=8 TeV with the ATLAS detector T2 - J. High Energy Phys. JO - Journal of High Energy Physics SP - 148 EP - 54pp VL - 08 IS - 8 PB - Springer KW - Exotics KW - Hadron-Hadron Scattering KW - Top physics AB - A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb(-1) of proton-proton collision data collected at a centre-of-mass energy of root s = 8TeV. The lepton-plus-jets final state is used, where the top pair decays to W (+) bW(-)(b) over bar, with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with Gamma/m = 15% decaying to tt. These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV. SN - 1029-8479 UR - http://arxiv.org/abs/1505.07018 UR - https://doi.org/10.1007/JHEP08(2015)148 DO - 10.1007/JHEP08(2015)148 LA - English N1 - WOS:000363532500006 ID - ATLASCollaborationAad_etal2015 ER -