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Search of new resonances decaying into top quark pairs with the ATLAS detector at the LHC and jet calibration studies

Abstract : The Standard Model (SM) of particle physics summarizes the current knowledge of subatomic physics and the known fundamental interactions (except for the gravitation). Up to now there is no experimental result that strongly contradicts the SM predictions. However, there are still some missing pieces in the SM of experimental or theoretical nature. Several physical models, known as Beyond-the-SM (BSM) theories, has been proposed in the last decades to try to account for one or more of the SM's open questions. Some of these theories as the topcolor model, chiral color models and Randall-Sundrum models with warped extra dimensionas predict the existence of new particles that couple strongly to the top quark, due to its high mass. This coupling implies that they decay primarily to top-quark pairs, t tbar. To test the validity of the SM and/or of the BSM theories, high energy accelerators of the TeV order are needed, as well as detectors adapted to analyse the collected events. Therefore, several searches for t tbar resonances have been performed at hadron-hadron colliders as the Tevatron or the Large Hadron Collider (LHC). The benchmark models considered are a topcolor assisted technicolor (TC2) which produces a topphilic Z' particle (used as benchmark for narrow t tbar resonances) and a Randall-Sundrum (RS) warped extra-dimension that would result in a bulk Kaluza-Klein (KK) gluon (used as benchmark for wide t tbar resonances). The topcolor assisted technicolor model explain the top mass and electroweak symmetry breaking through top quark condensation associated with symmetry breaking of a new strong force. The Randall-Sundrum model with a single extra warped extra dimension explain the hierarchy problem by allowing the gravity to propagate in the added warped dimension. The CDF and DØ collaborations have excluded a leptophobic topcolor Z' with mass smaller than 900 GeV at 95% C.L. At the LHC, the best limit obtained for the Z' and the KK gluon has been obtained by the CMS experiment using 2011 data, 500 < mZ' < 1300 GeV and 1000 < mgKK < 1400 GeV, respectively.
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Submitted on : Tuesday, October 30, 2012 - 3:28:26 PM
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  • HAL Id : tel-00747143, version 1


Reina Camacho. Search of new resonances decaying into top quark pairs with the ATLAS detector at the LHC and jet calibration studies. High Energy Physics - Experiment [hep-ex]. Université Blaise Pascal - Clermont-Ferrand II, 2012. English. ⟨tel-00747143⟩



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