A SEARCH FOR NEW QUARKS AND LEPTONS FROM Z ° DECAY AT LEP ALEPH Collaboration

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 Zj 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)

1 LAPP - Laboratoire d'Annecy de Physique des Particules
2 CERN - European Organization for Nuclear Research
3 CPPM - Centre de Physique des Particules de Marseille
4 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
5 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
6 LAL - Laboratoire de l'Accélérateur Linéaire
7 CEN Saclay

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.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

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, 1990, 236 (4), pp.511-522. ⟨10.1016/0370-2693(90)90392-J⟩. ⟨in2p3-00012126⟩