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D Decamp 1 B Deschizeaux 1 J.-P Lees 1 M.-N Minard 1 M Delfino E Fernandez M Martinez R Miquel S Orteu A Pacheco E Tubau M De A Farilla G Iaselli G Maggi S Natali S Nuzzo A Ranieri G Raso F Romano F Ruggieri G Selvaggi L Silvestris P Tempesta G Zito H Hu D Huang J Lin T Ruan T Wang W Wu Y Xie D Xu R Xu J Zhang W Zhao H Albrecht F Bird E Blucher T Charity H Drevermann L1 Garrido C Grab R Hagelberg S Haywood B Jost M Kasemann G Kellner J Knobloch A Lacourt I Lehraus T Lohse D Loke A Marchioro P Mato J May A Minten A Miotto P Palazzi M Pepe-Altarelli 2 F Ranjard Andrea Roth J Rothberg H Rotscheidt D Schlatter M Takashima M. Talby 3 H Taureg W Tejessy H Wachsmuth S Wheeler W Wiedenmann W Witzeling J Wotschack Pierre Henrard 4 P. Perret 4 Ziad Ajaltouni 4 Alain Falvard 4 M. Bardadin-Otwinowska 4 Pascal Gay 4 J. Jousset 4 B. Michel 4 Jean-Claude Montret 4 D. Pallin 4 Joseph Proriol 4 F. Prulhiere 4 Badier J. 5 Blondel A. 5 Bonneaud G. 5 Bourotte J. 5 Braems F. 5 Brient J.C. 5 Ciocci M.A. Fouque G. 5 Guirlet R. 5 Rougé A. 5 Rumpf M. 5 Tanaka R. 5 Videau H. 5 I Videau 5 L. Bellantoni J.F. Boudreau D. Cinabro J.S. Conway D.F. Cowen Z. Feng J.L. Harton J. Hilgart R.C. Jared R.P. Johnson B.W. Leclaire Y.B. Pan T. Parker J.R. Pater Y. Saadi V. Sharma J.A. Wear F.V. Weber Sau Lan Wu S.T. Xue G. Zobernig H. Albrecht W.B. Atwood F. Bird E. Blucher T.H. Burnett H. Drevermann L. Garrido C. Grab R. Hagelberg S. Haywood B. Jost M. Kasemann G. Kellner J. Knobloch A. Lacourt I. Lehraus T. Lohse D. Loke A. Marchioro P. Mato J. May A. Minten A. Miotto P. Palazzi M. Pepe-Altarelli 2 F. Ranjard A. Roth J. Rothberg H. Rotscheidt W. von Roden R. St.Denis D. Schlatter M. Takashima W. Tejessy H. Wachsmuth S. Wheeler W. Wiedenmann W. Witzeling J. Wotschack M.G. Catanesi M. De Palma A. Farilla G. Iaselli G. Maggi S. Natali S. Nuzzo A. Ranieri G. Raso F. Romano F. Ruggieri G. Selvaggi L. Silvestris P. Tempesta G. Zito J.M. Crespo M. Delfino E. Fernandez Ll.M. Mir J.A. Perlas V. Bertin 6 G. Aubourg 7
Abstract : A search for Z0 decays into pairs of possible new heavy quarks (t and b′), new heavy charged leptons (L±), stable heavy neutral leptons (νL) and unstable heavy neutral leptons (L0) is performed on data collected by the ALEPH detector corresponding to 11 550 events of Z0→hadrons. The limits on the masses of the heavy quarks are Mt > 45.8 GeV and Mb′ > 46.0 GeV, allowing for both charged-current and flavor-changing neutral-current decays of the b′. If an L± decays into a stable νL, then for MνL<42.7 GeV, the mass of L± is excluded for all values of ML± > MνL. Finally, while the mass of the stable νL is excluded up to 42.7 GeV, the mass of the unstable L0 is excluded up to 45.7 GeV with the mixing parameters |UℓL0|2 down to 10−13 at this mass. For 25.0 GeV < ML0 < 42.7 GeV, all values of |UℓL0|2 are excluded. All limits are given at 95% CL.
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D Decamp, B Deschizeaux, J.-P Lees, M.-N Minard, M Delfino, et al.. A SEARCH FOR NEW QUARKS AND LEPTONS FROM Z ° DECAY AT LEP ALEPH Collaboration. Physics Letters B, Elsevier, 1990, 236 (4), pp.511-522. ⟨10.1016/0370-2693(90)90392-J⟩. ⟨in2p3-00012126⟩



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