A precise measurement of Γ<inf>Z→bb</inf>/Γ<inf>Z→hadrons</inf>

D. Buskulic, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J. P. Lees, M. N. Minard, B. Pietrzyk, F. Ariztizabal, P. Comas, J. M. Crespo, M. Delfino, I. Efthymiopoulos, E. Fernandez, M. Fernandez-Bosman, V. Gaitan, Ll Garrido, T. Mattison, A. Pacheco, C. PadillaA. Pascual, D. Creanza, M. de Palma, A. Farilla, G. Iaselli, G. Maggi, S. Natali, S. Nuzzo, M. Quattromini, A. Ranieri, G. Raso, F. Romano, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, G. Zito, Y. Chai, H. Hu, D. Huang, X. Huang, J. Lin, T. Wang, Y. Xie, D. Xu, R. Xu, J. Zhang, L. Zhang, W. Zhao, E. Blucher, G. Bonvicini, J. Boudreau, D. Casper, H. Drevermann, R. W. Forty, G. Ganis, C. Gay, R. Hagelberg, J. Harvey, J. Hilgart, R. Jacobsen, B. Jost, J. Knobloch, I. Lehraus, T. Lohse, M. Maggi, C. Markou, M. Martinez, P. Mato, H. Meinhard, A. Minten, A. Miotto, R. Miquel, H. G. Moser, P. Palazzi, J. R. Pater, J. A. Perlas, J. F. Pusztaszeri, F. Ranjard, G. Redlinger, L. Rolandi, J. Rothberg, T. Ruan, M. Saich, D. Schlatter, M. Schmelling, F. Sefkow, W. Tejessy, I. R. Tomalin, R. Veenhof, H. Wachsmuth, S. Wasserbaech, W. Wiedenmann, T. Wildish, W. Witzeling, J. Wotschack, Z. Ajaltouni, F. Badaud, M. Bardadin-Otwinowska, R. El Fellous

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180 Citations (Scopus)

Abstract

A measurement of the partial width ratio Γbb Γhad using a method which tags the Z → bb decays through the lif etime of the produced heavy hadrons is presented. This method relies on the tracking precision afforded by a double-sided silicon vertex detector. The tag algorithm makes a probabilistic interpretation of three-dimensional track impact parameters, using the data to measure the resolution. By tagging the two b hadrons separately, both Γbb Γhad and the tag efficiency can be determined from the data. For a 26% efficiency of tagging a single b hadron within the vertex detector solid angle coverage, a purity of 96% is achieved. A value of Γbb Γhad = 0.2192±0.0026(stat.)±0.0016(Γcc/ Γhad) is found. Combining this result with other recent ALEPH Γbb Γhad measurements gives a 95% confidence upper limit on the Standard Model top mass of Mt < 228 GeV. © 1993.
Original languageEnglish
Pages (from-to)535-548
JournalPhysics Letters B
Volume313
Issue number3-4
DOIs
Publication statusPublished - 2 Sep 1993

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