[PDF] Search For Excited Leptons With The Atlas Detector eBook

Author :
Publisher :
Page : 54 pages
File Size : 10,4 MB
Release : 2016
Category :
ISBN :

GET BOOK

Our search for compositeness of electrons and muons is presented using a data sample of proton-proton collisions at a center-of-mass energy of √(s) = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb-1. Excited leptons (l*) produced via contact interactions in conjunction with a standard model lepton are considered, and a search is made for their gauge decay modes. The decays considered are l* →l? and l* → lZ, which give final states of two leptons and a photon or, depending on the Z-boson decay mode, four leptons or two leptons and two jets. The number of events observed in data is consistent with the standard model prediction. Exclusion limits are set on the excited lepton mass, and the compositeness scale L. For the case Ml* = L the existence of excited electrons (muons) is excluded up to masses of 2.45 (2.47) TeV at 95% confidence level. The neutral current decays of excited leptons are considered for the first time, and limits are extended to include the possibility that the weight factors f and f ', which determine the couplings between standard model leptons and excited leptons via gauge mediated interactions, have opposite sign.

Author :
Publisher :
Page : 29 pages
File Size : 35,14 MB
Release : 2011
Category :
ISBN :

GET BOOK

A search for excited leptons is carried out with the CMS detector at the LHC, using 36 inverse picobarns of pp collision data recorded at sqrt(s) = 7 TeV. The search is performed for associated production of a lepton and an oppositely charged excited lepton pp to l l*, followed by the decay l* to l gamma, resulting in the l l gamma final state, where l = electron or muon. No excess of events above the standard model expectation is observed. Interpreting the findings in the context of l* production through four-fermion contact interactions and subsequent decay via electroweak processes, first upper limits are reported for l* production at this collision energy. The exclusion region in the compositeness scale Lambda and excited lepton mass M(l*) parameter space is extended beyond previously established limits. For Lambda = M(l*), excited lepton masses are excluded below 1070 GeV/c2̂ for e* and 1090 GeV/c2̂ for mu* at the 95% confidence level.

Author : Brigitte Marie Christine Vachon
Publisher :
Page : pages
File Size : 24,36 MB
Release : 2002
Category :
ISBN :

GET BOOK

A search for evidence that fundamental particles are made of smaller subconstituents is performed. The existence of excited states of fundamental particles would be an unambiguous indication of their composite nature. Experimental signatures compatible with the production of excited states of charged leptons in electron-positron collisions are studied. The data analysed were collected by the OPAL detector at the LEP collider. No evidence for the existence of excited states of charged leptons was found. Upper limits on the product of the cross-section and the electromagnetic branching fraction are inferred. Using results from the search for singly produced excited leptons, upper limits on the ratio of the excited lepton coupling constant to the compositeness scale are calculated. From pair production searches, 95% confidence level lower limits on the masses of excited electrons, muons and taus are determined to be 103.2 GeV.