Search for a fourth generation b’-quark at LEP-II at 196–209 GeV

J. Abdallah; P. Abreu; W. Adam; P. Adzic; T. Albrecht; R. Alemany-Fernandez; T. Allmendinger; P.P. Allport; U. Amaldi; N. Amapane; S. Amato; E. Anashkin; A. Andreazza; S. Andringa; N. Anjos; P. Antilogus; W.-D. Apel; Y. Arnoud; S. Ask; B. Asman; J.E. Augustin; A. Augustinus; P. Baillon; A. Ballestrero; P. Bambade; R. Barbier; D. Bardin; G.J. Barker; A. Baroncelli; M. Battaglia; M. Baubillier; K-H. Becks; M. Begalli; A. Behrmann; E. Ben-Haim; N. Benekos; A. Benvenuti; C. Berat; M. Berggren; L. Berntzon; D. Bertrand; M. Besancon; N. Besson; D. Bloch; M. Blom; M. Bluj; M. Bonesini; M. Boonekamp; P.S.L. Booth; G. Borisov; O. Botner; B. Bouquet; T.J.V. Bowcock; I. Boyko; M. Bracko; R. Brenner; E. Brodet; P. Bruckman; J.M. Brunet; B. Buschbeck; P. Buschmann; M. Calvi; T. Camporesi; V. Canale; F. Carena; N. Castro; F. Cavallo; M. Chapkin; Ph. Charpentier; P. Checchia; R. Chierici; P. Chliapnikov; J. Chudoba; S.U. Chung; K. Cieslik; P. Collins; R. Contri; G. Cosme; F. Cossutti; M.J. Costa; D. Crennell; J. Cuevas; J. D’Hondt; J. Dalmau; T. Da Silva; W. Da Silva; G. Della Ricca; A. De Angelis; W. De Boer; C. De Clercq; B. De Lotto; N. De Maria; A. De Min; L. de Paula; L. Di Ciaccio; A. Di Simone; K. Doroba; J. Drees; G. Eigen; T. Ekelof; M. Ellert; M. Elsing; M.C. Espirito Santo; G. Fanourakis; D. Fassouliotis; M. Feindt; J. Fernandez; A. Ferrer; F. Ferro; U. Flagmeyer; H. Foeth; E. Fokitis; F. Fulda-Quenzer; J. Fuster; M. Gandelman; C. Garcia; Ph. Gavillet; E. Gazis; R. Gokieli; B. Golob; G. Gomez-Ceballos; P. Goncalves; E. Graziani; G. Grosdidier; K. Grzelak; J. Guy; C. Haag; A. Hallgren; K. Hamacher; K. Hamilton; S. Haug; F. Hauler; V. Hedberg; M. Hennecke; H. Herr; J. Hoffman; S-O. Holmgren; P.J. Holt; M.A. Houlden; J.N. Jackson; G. Jarlskog; P. Jarry; D. Jeans; E.K. Johansson; P.D. Johansson; P. Jonsson; C. Joram; L. Jungermann; F. Kapusta; S. Katsanevas; E. Katsoufis; G. Kernel; B.P. Kersevan; U. Kerzel; B.T. King; N.J. Kjaer; P. Kluit; P. Kokkinias; C. Kourkoumelis; O. Kouznetsov; Z. Krumstein; M. Kucharczyk; J. Lamsa; G. Leder; F. Ledroit; L. Leinonen; R. Leitner; J. Lemonne; V. Lepeltier; T. Lesiak; W. Liebig; D. Liko; A. Lipniacka; J.H. Lopes; J.M. Lopez; D. Loukas; P. Lutz; L. Lyons; J. MacNaughton; A. Malek; S. Maltezos; F. Mandl; J. Marco; R. Marco; B. Marechal; M. Margoni; J-C. Marin; C. Mariotti; A. Markou; C. Martinez-Rivero; J. Masik; N. Mastroyiannopoulos; F. Matorras; C. Matteuzzi; F. Mazzucato; M. Mazzucato; R. Mc Nulty; C. Meroni; E. Migliore; W. Mitaroff; U. Mjoernmark; T. Moa; M. Moch; K. Moenig; R. Monge; J. Montenegro; D. Moraes; S. Moreno; P. Morettini; U. Mueller; K. Muenich; M. Mulders; L. Mundim; W. Murray; B. Muryn; G. Myatt; T. Myklebust; M. Nassiakou; F. Navarria; K. Nawrocki; R. Nicolaidou; M. Nikolenko; A. Oblakowska-Mucha; V. Obraztsov; O. Oliveira; S.M. Oliveira; A. Olshevski; A. Onofre; R. Orava; K. Osterberg; A. Ouraou; A. Oyanguren; M. Paganoni; S. Paiano; J.P. Palacios; H. Palka; Th.D. Papadopoulou; L. Pape; C. Parkes; F. Parodi; U. Parzefall; A. Passeri; O. Passon; L. Peralta; V. Perepelitsa; A. Perrotta; A. Petrolini; J. Piedra; L. Pieri; F. Pierre; M. Pimenta; E. Piotto; T. Podobnik; V. Poireau; M.E. Pol; G. Polok; V. Pozdniakov; N. Pukhaeva; A. Pullia; J. Rames; A. Read; P. Rebecchi; J. Rehn; D. Reid; R. Reinhardt; P. Renton; F. Richard; J. Ridky; M. Rivero; D. Rodriguez; A. Romero; P. Ronchese; P. Roudeau; T. Rovelli; V. Ruhlmann-Kleider; D. Ryabtchikov; A. Sadovsky; L. Salmi; J. Salt; C. Sander; R. Santos; A. Savoy-Navarro; U. Schwickerath; R. Sekulin; M. Siebel; A. Sisakian; G. Smadja; O. Smirnova; A. Sokolov; A. Sopczak; R. Sosnowski; T. Spassov; M. Stanitzki; A. Stocchi; J. Strauss; B. Stugu; M. Szczekowski; M. Szeptycka; T. Szumlak; T. Tabarelli; A.C. Taffard; F. Tegenfeldt; J. Timmermans; L. Tkatchev; M. Tobin; S. Todorovova; B. Tome; A. Tonazzo; P. Tortosa; P. Travnicek; D. Treille; G. Tristram; M. Trochimczuk; C. Troncon; M-L. Turluer; I.A. Tyapkin; P. Tyapkin; S. Tzamarias; V. Uvarov; G. Valenti; P. Van Dam; J. Van Eldik; N. Van Remortel; I. Van Vulpen; G. Vegni; F. Veloso; W. Venus; P. Verdier; V. Verzi; D. Vilanova; L. Vitale; V. Vrba; H. Wahlen; A.J. Washbrook; C. Weiser; D. Wicke; J. Wickens; G. Wilkinson; M. Winter; M. Witek; O. Yushchenko; A. Zalewska; P. Zalewski; D. Zavrtanik; V. Zhuravlov; N.I. Zimin; A. Zintchenko; M. Zupan

doi:10.1140/epjc/s10052-007-0273-z

2021 Impact factor 4.991

Particles and Fields

Eur. Phys. J. C (2007) 50: 507-518
https://doi.org/10.1140/epjc/s10052-007-0273-z

Regular Article - Experimental Physics

Search for a fourth generation b’-quark at LEP-II at 196–209 GeV

J. Abdallah²⁶, P. Abreu²³, W. Adam⁵⁵, P. Adzic¹², T. Albrecht¹⁸, R. Alemany-Fernandez⁹, T. Allmendinger¹⁸, P.P. Allport²⁴, U. Amaldi³⁰, N. Amapane⁴⁸, S. Amato⁵², E. Anashkin³⁷, A. Andreazza²⁹, S. Andringa²³, N. Anjos²³, P. Antilogus²⁶, W.-D. Apel¹⁸, Y. Arnoud¹⁵, S. Ask²⁷, B. Asman⁴⁷, J.E. Augustin²⁶, A. Augustinus⁹, P. Baillon⁹, A. Ballestrero⁴⁹, P. Bambade²¹, R. Barbier²⁸, D. Bardin¹⁷, G.J. Barker⁵⁷, A. Baroncelli⁴⁰, M. Battaglia⁹, M. Baubillier²⁶, K-H. Becks⁵⁸, M. Begalli⁷, A. Behrmann⁵⁸, E. Ben-Haim²¹, N. Benekos³³, A. Benvenuti⁵, C. Berat¹⁵, M. Berggren²⁶, L. Berntzon⁴⁷, D. Bertrand², M. Besancon⁴¹, N. Besson⁴¹, D. Bloch¹⁰, M. Blom³², M. Bluj⁵⁶, M. Bonesini³⁰, M. Boonekamp⁴¹, P.S.L. Booth²⁴, G. Borisov²², O. Botner⁵³, B. Bouquet²¹, T.J.V. Bowcock²⁴, I. Boyko¹⁷, M. Bracko⁴⁴, R. Brenner⁵³, E. Brodet³⁶, P. Bruckman¹⁹, J.M. Brunet⁸, B. Buschbeck⁵⁵, P. Buschmann⁵⁸, M. Calvi³⁰, T. Camporesi⁹, V. Canale³⁹, F. Carena⁹, N. Castro²³, F. Cavallo⁵, M. Chapkin⁴³, Ph. Charpentier⁹, P. Checchia³⁷, R. Chierici⁹, P. Chliapnikov⁴³, J. Chudoba⁹, S.U. Chung⁹, K. Cieslik¹⁹, P. Collins⁹, R. Contri¹⁴, G. Cosme²¹, F. Cossutti⁵⁰, M.J. Costa⁵⁴, D. Crennell³⁸, J. Cuevas³⁵, J. D’Hondt², J. Dalmau⁴⁷, T. Da Silva⁵², W. Da Silva²⁶, G. Della Ricca⁵⁰, A. De Angelis⁵¹, W. De Boer¹⁸, C. De Clercq², B. De Lotto⁵¹, N. De Maria⁴⁸, A. De Min³⁷, L. de Paula⁵², L. Di Ciaccio³⁹, A. Di Simone⁴⁰, K. Doroba⁵⁶, J. Drees⁵⁸^,9, G. Eigen⁴, T. Ekelof⁵³, M. Ellert⁵³, M. Elsing⁹, M.C. Espirito Santo²³, G. Fanourakis¹², D. Fassouliotis¹²^,3, M. Feindt¹⁸, J. Fernandez⁴², A. Ferrer⁵⁴, F. Ferro¹⁴, U. Flagmeyer⁵⁸, H. Foeth⁹, E. Fokitis³³, F. Fulda-Quenzer²¹, J. Fuster⁵⁴, M. Gandelman⁵², C. Garcia⁵⁴, Ph. Gavillet⁹, E. Gazis³³, R. Gokieli⁹^,56, B. Golob⁴⁴^,46, G. Gomez-Ceballos⁴², P. Goncalves²³, E. Graziani⁴⁰, G. Grosdidier²¹, K. Grzelak⁵⁶, J. Guy³⁸, C. Haag¹⁸, A. Hallgren⁵³, K. Hamacher⁵⁸, K. Hamilton³⁶, S. Haug³⁴, F. Hauler¹⁸, V. Hedberg²⁷, M. Hennecke¹⁸, H. Herr⁹, J. Hoffman⁵⁶, S-O. Holmgren⁴⁷, P.J. Holt⁹, M.A. Houlden²⁴, J.N. Jackson²⁴, G. Jarlskog²⁷, P. Jarry⁴¹, D. Jeans³⁶, E.K. Johansson⁴⁷, P.D. Johansson⁴⁷, P. Jonsson²⁸, C. Joram⁹, L. Jungermann¹⁸, F. Kapusta²⁶, S. Katsanevas²⁸, E. Katsoufis³³, G. Kernel⁴⁴, B.P. Kersevan⁴⁴^,46, U. Kerzel¹⁸, B.T. King²⁴, N.J. Kjaer⁹, P. Kluit³², P. Kokkinias¹², C. Kourkoumelis³, O. Kouznetsov¹⁷, Z. Krumstein¹⁷, M. Kucharczyk¹⁹, J. Lamsa¹, G. Leder⁵⁵, F. Ledroit¹⁵, L. Leinonen⁴⁷, R. Leitner³¹, J. Lemonne², V. Lepeltier²¹, T. Lesiak¹⁹, W. Liebig⁵⁸, D. Liko⁵⁵, A. Lipniacka⁴⁷, J.H. Lopes⁵², J.M. Lopez³⁵, D. Loukas¹², P. Lutz⁴¹, L. Lyons³⁶, J. MacNaughton⁵⁵, A. Malek⁵⁸, S. Maltezos³³, F. Mandl⁵⁵, J. Marco⁴², R. Marco⁴², B. Marechal⁵², M. Margoni³⁷, J-C. Marin⁹, C. Mariotti⁹, A. Markou¹², C. Martinez-Rivero⁴², J. Masik¹³, N. Mastroyiannopoulos¹², F. Matorras⁴², C. Matteuzzi³⁰, F. Mazzucato³⁷, M. Mazzucato³⁷, R. Mc Nulty²⁴, C. Meroni²⁹, E. Migliore⁴⁸, W. Mitaroff⁵⁵, U. Mjoernmark²⁷, T. Moa⁴⁷, M. Moch¹⁸, K. Moenig⁹^,11, R. Monge¹⁴, J. Montenegro³², D. Moraes⁵², S. Moreno²³, P. Morettini¹⁴, U. Mueller⁵⁸, K. Muenich⁵⁸, M. Mulders³², L. Mundim⁷, W. Murray³⁸, B. Muryn²⁰, G. Myatt³⁶, T. Myklebust³⁴, M. Nassiakou¹², F. Navarria⁵, K. Nawrocki⁵⁶, R. Nicolaidou⁴¹, M. Nikolenko¹⁷^,10, A. Oblakowska-Mucha²⁰, V. Obraztsov⁴³, O. Oliveira²³, S.M. Oliveira²³, A. Olshevski¹⁷, A. Onofre²³, R. Orava¹⁶, K. Osterberg¹⁶, A. Ouraou⁴¹, A. Oyanguren⁵⁴, M. Paganoni³⁰, S. Paiano⁵, J.P. Palacios²⁴, H. Palka¹⁹, Th.D. Papadopoulou³³, L. Pape⁹, C. Parkes²⁵, F. Parodi¹⁴, U. Parzefall⁹, A. Passeri⁴⁰, O. Passon⁵⁸, L. Peralta²³, V. Perepelitsa⁵⁴, A. Perrotta⁵, A. Petrolini¹⁴, J. Piedra⁴², L. Pieri⁴⁰, F. Pierre⁴¹, M. Pimenta²³, E. Piotto⁹, T. Podobnik⁴⁴^,46, V. Poireau⁹, M.E. Pol⁶, G. Polok¹⁹, V. Pozdniakov¹⁷, N. Pukhaeva¹⁷, A. Pullia³⁰, J. Rames¹³, A. Read³⁴, P. Rebecchi⁹, J. Rehn¹⁸, D. Reid³², R. Reinhardt⁵⁸, P. Renton³⁶, F. Richard²¹, J. Ridky¹³, M. Rivero⁴², D. Rodriguez⁴², A. Romero⁴⁸, P. Ronchese³⁷, P. Roudeau²¹, T. Rovelli⁵, V. Ruhlmann-Kleider⁴¹, D. Ryabtchikov⁴³, A. Sadovsky¹⁷, L. Salmi¹⁶, J. Salt⁵⁴, C. Sander¹⁸, R. Santos²³, A. Savoy-Navarro²⁶, U. Schwickerath⁹, R. Sekulin³⁸, M. Siebel⁵⁸, A. Sisakian¹⁷, G. Smadja²⁸, O. Smirnova²⁷, A. Sokolov⁴³, A. Sopczak²², R. Sosnowski⁵⁶, T. Spassov⁹, M. Stanitzki¹⁸, A. Stocchi²¹, J. Strauss⁵⁵, B. Stugu⁴, M. Szczekowski⁵⁶, M. Szeptycka⁵⁶, T. Szumlak²⁰, T. Tabarelli³⁰, A.C. Taffard²⁴, F. Tegenfeldt⁵³, J. Timmermans³²^*, L. Tkatchev¹⁷, M. Tobin²⁴, S. Todorovova¹³, B. Tome²³, A. Tonazzo³⁰, P. Tortosa⁵⁴, P. Travnicek¹³, D. Treille⁹, G. Tristram⁸, M. Trochimczuk⁵⁶, C. Troncon²⁹, M-L. Turluer⁴¹, I.A. Tyapkin¹⁷, P. Tyapkin¹⁷, S. Tzamarias¹², V. Uvarov⁴³, G. Valenti⁵, P. Van Dam³², J. Van Eldik⁹, N. Van Remortel¹⁶, I. Van Vulpen⁹, G. Vegni²⁹, F. Veloso²³, W. Venus³⁸, P. Verdier²⁸, V. Verzi³⁹, D. Vilanova⁴¹, L. Vitale⁵⁰, V. Vrba¹³, H. Wahlen⁵⁸, A.J. Washbrook²⁴, C. Weiser¹⁸, D. Wicke⁹, J. Wickens², G. Wilkinson³⁶, M. Winter¹⁰, M. Witek¹⁹, O. Yushchenko⁴³, A. Zalewska¹⁹, P. Zalewski⁵⁶, D. Zavrtanik⁴⁵, V. Zhuravlov¹⁷, N.I. Zimin¹⁷, A. Zintchenko¹⁷, M. Zupan¹² and The DELPHI Collaboration

¹ Department of Physics and Astronomy, Iowa State University, Ames, AI, 50011-3160, USA
² IIHE, ULB-VUB, Pleinlaan 2, 1050, Brussels, Belgium
³ Physics Laboratory, University of Athens, Solonos Str. 104, 10680, Athens, Greece
⁴ Department of Physics, University of Bergen, Allégaten 55, 5007, Bergen, Norway
⁵ Dipartimento di Fisica, Università di Bologna and INFN, Via Irnerio 46, 40126, Bologna, Italy
⁶ Centro Brasileiro de Pesquisas Físicas, rua Xavier Sigaud 150, 22290, Rio de Janeiro, Brazil
⁷ Inst. de Física, Univ. Estadual do Rio de Janeiro, rua São Francisco Xavier 524, Rio de Janeiro, Brazil
⁸ Lab. de Physique Corpusculaire, IN2P3-CNRS, Collège de France, 75231, Paris Cedex 05, France
⁹ CERN, 1211, Geneva 23, Switzerland
¹⁰ Institut de Recherches Subatomiques, IN2P3 - CNRS/ULP - BP20, 67037, Strasbourg Cedex, France
¹¹ DESY-Zeuthen, Platanenallee 6, 15735, Zeuthen, Germany
¹² Institute of Nuclear Physics, N.C.S.R. Demokritos, P.O. Box 60228, 15310, Athens, Greece
¹³ Inst. of Phys. of the C.A.S. High Energy Physics Division, FZU, Na Slovance 2, 18040, Praha 8, Czech Republic
¹⁴ Dipartimento di Fisica, Università di Genova and INFN, Via Dodecaneso 33, 16146, Genova, Italy
¹⁵ Institut des Sciences Nucléaires, IN2P3-CNRS, Université de Grenoble 1, 38026, Grenoble Cedex, France
¹⁶ Helsinki Institute of Physics and Department of Physical Sciences, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland
¹⁷ Head Post Office, Joint Institute for Nuclear Research, Dubna, P.O. Box 79, 101000, Moscow, Russia
¹⁸ Institut für Experimentelle Kernphysik, Universität Karlsruhe, Postfach 6980, 76128, Karlsruhe, Germany
¹⁹ Institute of Nuclear Physics PAN, Ul. Radzikowskiego 152, 31142, Krakow, Poland
²⁰ Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, 30055, Krakow, Poland
²¹ Lab. de l’Accélérateur Linéaire, IN2P3-CNRS, Université de Paris-Sud, , Bât. 200, 91405, Orsay Cedex, France
²² School of Physics and Chemistry, University of Lancaster, Lancaster, LA1 4YB, UK
²³ LIP, FCUL, IST, CFCUC, Av. Elias Garcia 14-1o, 1000, Lisboa Codex, Portugal
²⁴ Department of Physics, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX, UK
²⁵ Dept. of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ, UK
²⁶ LPNHE, IN2P3-CNRS, Univ. Paris VI et VII, Tour 33 (RdC), 4 place Jussieu, 75252, Paris Cedex 05, France
²⁷ Department of Physics, University of Lund, Sölvegatan 14, 22363, Lund, Sweden
²⁸ IPNL, IN2P3-CNRS, Université Claude Bernard de Lyon, 69622, Villeurbanne Cedex, France
²⁹ Dipartimento di Fisica, Università di Milano and INFN-MILANO, Via Celoria 16, 20133, Milan, Italy
³⁰ Dipartimento di Fisica, Univ. di Milano-Bicocca and INFN-MILANO, Piazza della Scienza 3, 20126, Milan, Italy
³¹ IPNP of MFF, Charles Univ., Areal MFF, V Holesovickach 2, 18000, Praha 8, Czech Republic
³² NIKHEF, Postbus 41882, 1009 DB, Amsterdam, The Netherlands
³³ Physics Department, National Technical University, Zografou Campus, 15773, Athens, Greece
³⁴ Physics Department, University of Oslo, Oslo, 0316, Norway
³⁵ Dpto. Fisica, Univ. Oviedo, Avda. Calvo Sotelo s/n, 33007, Oviedo, Spain
³⁶ Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK
³⁷ Dipartimento di Fisica, Università di Padova and INFN, Via Marzolo 8, 35131, Padua, Italy
³⁸ Rutherford Appleton Laboratory, Chilton, Didcot, OX11 OQX, UK
³⁹ Dipartimento di Fisica, Università di Roma II and INFN, Tor Vergata, 00173, Rome, Italy
⁴⁰ Dipartimento di Fisica, Università di Roma III and INFN, Via della Vasca Navale 84, 00146, Rome, Italy
⁴¹ DAPNIA/Service de Physique des Particules, CEA-Saclay, 91191, Gif-sur-Yvette Cedex, France
⁴² Instituto de Fisica de Cantabria (CSIC-UC), Avda. los Castros s/n, 39006, Santander, Spain
⁴³ Inst. for High Energy Physics, Serpukov, P.O. Box 35, Protvino, Moscow Region, Russia
⁴⁴ J. Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
⁴⁵ Laboratory for Astroparticle Physics, University of Nova Gorica, Kostanjeviska 16a, 5000, Nova Gorica, Slovenia
⁴⁶ Department of Physics, University of Ljubljana, 1000, Ljubljana, Slovenia
⁴⁷ Fysikum, Stockholm University, Box 6730, 11385, Stockholm, Sweden
⁴⁸ Dipartimento di Fisica Sperimentale, Università di Torino and INFN, Via P. Giuria 1, 10125, Turin, Italy
⁴⁹ INFN, Sezione di Torino and Dipartimento di Fisica Teorica, Università di Torino, Via Giuria 1, 10125, Turin, Italy
⁵⁰ Dipartimento di Fisica, Università di Trieste and INFN, Via A. Valerio 2, 34127, Trieste, Italy
⁵¹ Istituto di Fisica, Università di Udine and INFN, 33100, Udine, Italy
⁵² C.P. 68528 Cidade Univ., Ilha do Fundão, Univ. Federal do Rio de Janeiro, 21945-970, Rio de Janeiro, Brazil
⁵³ Department of Radiation Sciences, University of Uppsala, P.O. Box 535, 75121, Uppsala, Sweden
⁵⁴ IFIC, Valencia-CSIC, and D.F.A.M.N., U. de Valencia, Avda. Dr. Moliner 50, 46100, Burjassot, Valencia, Spain
⁵⁵ Institut für Hochenergiephysik, Österr. Akad. d. Wissensch., Nikolsdorfergasse 18, 1050, Vienna, Austria
⁵⁶ Inst. Nuclear Studies and University of Warsaw, Ul. Hoza 69, 00681, Warsaw, Poland
⁵⁷ University of Warwick, Coventry, CV4 7AL, UK
⁵⁸ Fachbereich Physik, University of Wuppertal, Postfach 100127, 42097, Wuppertal, Germany

^* e-mail: Jan.Timmermans@cern.ch

Received: 26 July 2006
Revised: 28 January 2007
Published online: 29 March 2007

Abstract

A search for the pair production of fourth generation b’-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging from 196 to 209 GeV, corresponding to an integrated luminosity of 420 pb^-1. No evidence for a signal was found. Upper limits on BR(b’→bZ) and BR(b’→cW) were obtained for b’ masses ranging from 96 to 103 GeV/c ². These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of , where V_cb′, V_tb′ and V_tb are elements of the extended CKM matrix.