1,384 research outputs found
Search for exotic particles in multileptonic final states with the ATLAS detector
No full textThe search for exotic particles Beyond the Standard Model (BSM) is a major part of the ATLAS physics program. Due to the low number of Standard Model events in final states with large lepton multiplicity, searches in these final states allow to reject a substantial fraction of background providing a better signal-to-noise ratio. New physics (NP) events are searched for in several processes:
production of doubly charged Higgs bosons (H±±) and production of heavy neutral or charged leptons predicted, for instance in mechanisms like Type-III SeeSaw or LRSM models. BSM searches in multileptonic finale states using the pp collision data sample collected in the Run2 by the ATLAS experiment corresponding to 80.0 fb−1 of integrated luminosity at a centre-of-mass energy of 13 TeV are presented. Final states with same-sign leptons (only electrons and muons) are particularly interesting since they are affected by low Standard Model background. Searches are performed in final states which maximize the predicted production cross-section
Search for Type-III SeeSaw heavy lepton with the ATLAS Detector at the LHC using =13 TeV up to 140 fb
No full textA search of heavy leptons and pair production predicted by the Type-III SeeSaw mechanism is presented. This mechanism extends the Standard Model, introducing at least two new triplets of fermionic fields with zero hypercharge in the adjoint representation of SU(2), resulting in two heavy Dirac charged leptons and a heavy Majorana neutral lepton. This search uses data collected by the ATLAS detector at the Large Hadron Collider in protonproton collision at a centre-of-mass energy of 13 TeV, with an integrated luminosity up to 140 fb corresponding to the full Run-2 dataset recorded between 2015-2018.The analysis focuses on all the possible production and boson decay channels of these heavy leptons, which are assumed to be degenerate in mass. The search is based on the separate optimization of each lepton multiplicity final state, considering 2, 3, 4 or more than 5 leptons. The power of the leptonic channels lies in the low expected background from Standard Model processes. Different control and signal regions are defined for each final state, designed to be orthogonal one each other. Good agreement between the number of events in data and Standard Model predictions is observed.The results are translated into exclusion limits on heavy lepton masses with a 95% confidence level using statistical uncertainties only. Assuming the branching ratios to all lepton flavours to be equal, a lower limit of 560 GeV is obtained
Il rinvio pregiudiziale come modello: l'introduzione di un meccanismo di coinvolgimento pregiudiziale della Corte di Cassazione nel giudizio civile
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La prima udienza di trattazione davanti al giudice istruttore ed il nuovo regime delle preclusioni nel processo di separazione (art. 709 bis c.p.c.)
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