A search for new particles that decay into top quark pairs (tt ¯ ) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7  fb −1 of proton–proton (pp ) collision data collected at a center-of-mass energy s √ =7  TeV . In the tt ¯ →WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The tt ¯ system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to the Standard Model expectation in the tt ¯ invariant mass spectrum is performed. No evidence for a tt ¯ resonance is found and 95% credibility-level limits on the production rate are determined for massive states predicted in two benchmark models. The upper limits on the cross section times branching ratio of a narrow Z ′ resonance range from 5.1 pb for a boson mass of 0.5 TeV to 0.03 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z ′ resonance with a mass below 1.74 TeV is excluded. Limits are also derived for a broad color-octet resonance with Γ/m=15.3% . A Kaluza–Klein excitation of the gluon in a Randall–Sundrum model is excluded for masses below 2.07 TeV.

G. Aad, E. Abat, B. Abbott, J. Abdallah, A.A. Abdelalim, A. Abdesselam, et al. (2013). Search for tt ¯ resonances in the lepton plus jets final state with ATLAS using 4.7  fb −1 of pp collisions at s √ =7  TeV. PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY, 88, 012004-1-012004-28 [10.1103/PhysRevD.88.012004].

Search for tt ¯ resonances in the lepton plus jets final state with ATLAS using 4.7  fb −1 of pp collisions at s √ =7  TeV

BELLAGAMBA, LORENZO;BERTIN, ANTONIO;BOSCHERINI, DAVIDE;BRUNI, ALESSIA;BRUNI, GRAZIANO;CAFORIO, DAVIDE;DE CASTRO, STEFANO;DI SIPIO, RICCARDO;FABBRI, LAURA;FRANCHINI, MATTEO;GIACOBBE, BENEDETTO;MASSA, IGNAZIO GIACOMO;MENGARELLI, ALBERTO;MONZANI, SIMONE;PICCININI, MAURIZIO;RINALDI, LORENZO;ROMANO, MARINO;SBARRA, CARLA;SBRIZZI, ANTONIO;SEMPRINI CESARI, NICOLA;SPIGHI, ROBERTO;VALENTINETTI, SARA;VILLA, MAURO;I. Vivarelli;ZOCCOLI, ANTONIO;
2013

Abstract

A search for new particles that decay into top quark pairs (tt ¯ ) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7  fb −1 of proton–proton (pp ) collision data collected at a center-of-mass energy s √ =7  TeV . In the tt ¯ →WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The tt ¯ system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to the Standard Model expectation in the tt ¯ invariant mass spectrum is performed. No evidence for a tt ¯ resonance is found and 95% credibility-level limits on the production rate are determined for massive states predicted in two benchmark models. The upper limits on the cross section times branching ratio of a narrow Z ′ resonance range from 5.1 pb for a boson mass of 0.5 TeV to 0.03 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z ′ resonance with a mass below 1.74 TeV is excluded. Limits are also derived for a broad color-octet resonance with Γ/m=15.3% . A Kaluza–Klein excitation of the gluon in a Randall–Sundrum model is excluded for masses below 2.07 TeV.
2013
G. Aad, E. Abat, B. Abbott, J. Abdallah, A.A. Abdelalim, A. Abdesselam, et al. (2013). Search for tt ¯ resonances in the lepton plus jets final state with ATLAS using 4.7  fb −1 of pp collisions at s √ =7  TeV. PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY, 88, 012004-1-012004-28 [10.1103/PhysRevD.88.012004].
G. Aad; E. Abat; B. Abbott; J. Abdallah; A.A. Abdelalim; A. Abdesselam; O. Abdinov; B. Abi; M. Abolins; H. Abramowicz; H. Abreu; E. Acerbi; B.S. Achar...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/221059
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