Search for scalar quarks in e+e- collisions at sqrt(s) up to 209GeV

Searches for scalar top, scalar bottom and mass-degenerate scalar quarks are performed in the data collected by the ALEPH detector at LEP, at centre-of-mass energies up to 209GeV, corresponding to an integrated luminosity of 675 pb. No evidence for the production of such particles is found in the decay channels t̃ → c/uχ, t̃ → blν̃, b̃ → bχ, q̃ → qχ or in the stop four-body decay channel t̃ → bχf f̄ ′ studied for the first time at LEP. The results of these searches yield improved mass lower limits. In particular, an absolute lower limit of 63GeV/c is obtained for the stop mass, at 95% confidence level, irrespective of the stop lifetime and decay branching ratios. (Submitted to Physics Letters B) ) See next pages for the list of authors The ALEPH Collaboration A. Heister, S. Schael Physikalisches Institut das RWTH-Aachen, D-52056 Aachen, Germany R. Barate, R. Brunelière, I. De Bonis, D. Decamp, C. Goy, S. Jezequel, J.-P. Lees, F. Martin, E. Merle, M.-N. Minard, B. Pietrzyk, B. Trocmé Laboratoire de Physique des Particules (LAPP), INP-CNRS, F-74019 Annecy-le-Vieux Cedex, France G. Boix, S. Bravo, M.P. Casado, M. Chmeissani, J.M. Crespo, E. Fernandez, M. Fernandez-Bosman, Ll. Garrido, E. Graugés, J. Lopez, M. Martinez, G. Merino, R. Miquel, Ll.M. Mir, A. Pacheco, D. Paneque, H. Ruiz Institut de Física d’Altes Energies, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Barcelona), Spain A. Colaleo, D. Creanza, N. De Filippis, M. de Palma, G. Iaselli, G. Maggi, M. Maggi, S. Nuzzo, A. Ranieri, G. Raso, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, A. Tricomi, G. Zito Dipartimento di Fisica, INFN Sezione di Bari, I-70126 Bari, Italy X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao Institute of High Energy Physics, Academia Sinica, Beijing, The People’s Republic of China D. Abbaneo, P. Azzurri, T. Barklow, O. Buchmüller, M. Cattaneo, F. Cerutti, B. Clerbaux, H. Drevermann, R.W. Forty, M. Frank, F. Gianotti, T.C. Greening, J.B. Hansen, J. Harvey, D.E. Hutchcroft, P. Janot, B. Jost, M. Kado, P. Mato, A. Moutoussi, F. Ranjard, L. Rolandi, D. Schlatter, G. Sguazzoni, W. Tejessy, F. Teubert, A. Valassi, I. Videau, J.J. Ward European Laboratory for Particle Physics (CERN), CH-1211 Geneva 23, Switzerland F. Badaud, S. Dessagne, A. Falvard, D. Fayolle, P. Gay, J. Jousset, B. Michel, S. Monteil, D. Pallin, J.M. Pascolo, P. Perret Laboratoire de Physique Corpusculaire, Université Blaise Pascal, INP-CNRS, Clermont-Ferrand, F-63177 Aubière, France J.D. Hansen, J.R. Hansen, P.H. Hansen, B.S. Nilsson Niels Bohr Institute, 2100 Copenhagen, DK-Denmark A. Kyriakis, C. Markou, E. Simopoulou, A. Vayaki, K. Zachariadou Nuclear Research Center Demokritos (NRCD), GR-15310 Attiki, Greece A. Blondel, J.-C. Brient, F. Machefert, A. Rougé, M. Swynghedauw, R. Tanaka H. Videau Laboratoire de Physique Nucléaire et des Hautes Energies, Ecole Polytechnique, INP-CNRS, F-91128 Palaiseau Cedex, France V. Ciulli, E. Focardi, G. Parrini Dipartimento di Fisica, Università di Firenze, INFN Sezione di Firenze, I-50125 Firenze, Italy A. Antonelli, M. Antonelli, G. Bencivenni, F. Bossi, G. Capon, V. Chiarella, P. Laurelli, G. Mannocchi, G.P. Murtas, L. Passalacqua Laboratori Nazionali dell’INFN (LNF-INFN), I-00044 Frascati, Italy J. Kennedy, J.G. Lynch, P. Negus, V. O’Shea, A.S. Thompson Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ,United Kingdom

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