Abstract
A measurement of\(\Gamma _{b\bar b} /\Gamma _{had} \equiv \Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)\) is presented using a “mixed tag” method involving the identification of\(Z^0 \to b\bar b\) events by two different techniques. The first uses the large impact parameter of tracks emerging from the decay ofb-flavoured hadrons and the second their semi-leptonic decay. The identification efficiencies are measured from the data using all possible combinations of the two tags in opposite hemispheres. The method is therefore insensitive to Monte Carlo modelling of bottom quark production and ofb-flavoured hadron production and decay properties, and depends only weakly on the simulation of the detector. The data sample collected by OPAL at LEP in 1990 and 1991 is considered. The result is:
where the systematic uncertainty due to the charm quark partial width has been separated from the other systematic uncertainties. Combination with previous OPAL measurements gives:
Similar content being viewed by others
References
A. Blondel, A. Djouadi, C. Verzegnasso: Phys. Lett. B293 (1992) 253; J. Bernabéu, A. Pich, A. Santamará: Nucl. Phys. B 363 (1991) 326; A. Djouadi et al.: Nucl. Phys. B 349 (1991) 48; B.W. Lynn, R.G. Stuart: Phys. Lett. B 252 (1990) 676; F. Boudjema, A. Djouadi, C. Verzegnassi: Phys. Lett. B 238 (1990) 423; W. Beenakker, W. Hollik: Z. Phys. C40 (1988) 141; J. Bernabéu, A. Pich, A. Santamaria: Phys. Lett. B 200 (1988) 569; A.A. Akhundov, D. Yu. Bardin, T. Riemann: Nucl. Phys. B 276 (1986) 1
R. Chivukula, S. Selipsky, E. Simmons: Phys. Rev. Lett. 69 (1992) 575; J. Layssac, F.M. Renard, C. Verzegnassi: Phys. Lett. B 287 (1992) 267; F.M. Renard, C. Verzegnassi: Phys. Lett. B 260 (1991) 225; M. Boulware, D. Finell: Phys. Rev. D44 (1991) 2054; E. Nardi, E. Roulet: Phys. Lett. B 248 (1990) 139; G. Girardi, W. Hollik, C. Verzegnassi: Phys. Lett. B 240 (1990) 492; P. Langacker, D. London: Phys. Rev. D 38 (1988) 886
DELPHI Coll., P. Abreu et al.: Z. Phys. C56 (1992) 47; OPAL Coll., P. Acton et al.: Z. Phys. C55 (1992) 191; OPAL Coll., M.Z. Akrawy et al.: Phys. Lett. B 263 (1991) 311; L3 Coll., B. Adeva et al.: Phys. Lett. B 261 (1991) 177; ALEPH Coll., D. Decamp et al.: Phys. Lett. 244B (1990) 551; L3 Coll., B. Adeva et al.: Phys. Lett. B241 (1990) 416; MARKII Coll., J.F. Kral et al.: Phys. Rev. Lett. 64 (1990) 1211
OPAL Coll., P. Acton et al.: Z. Phys. C58 (1993) 523
OPAL Coll., P. Acton et al.: Z. Phys. C60 (1993) 199
OPAL Coll., P. Acton et al.: Z. Phys. C60, (1993) 579
ALEPH Coll., D. Buskulic et al.: Phys. Lett. B313 (1993) 535; MARKII Coll., R. Jacobsen et al.: Phys. Rev. Lett. 67 (1991) 3347
ALEPH Coll., D. Buskulic et al.: Phys. Lett. B313 (1993) 549; L3 Coll., O. Adriani et al.: Phys. Lett. B 307 (1993) 237; DELPHI Coll., P. Abreu et al.: Phys. Lett. B 295 (1992) 383; DELPHI Coll., P. Abreu et al.: Phys. Lett. B 281 (1992) 383
OPAL Coll., K. Ahmet et al.: Nucl. Instrum. Methods A305 (1991) 275
P.P. Allport et al.: Nucl. Instrum. Methods A324 (1993) 34
M. Arignon et al.: Nucl. Instrum. Methods A324 (1992) 103
D.G. Charlton, F. Meijers, T.J. Smith, P.S. Wells: Nucl. Instrum. Methods A325 (1993) 129
OPAL Coll., G. Alexander et al.: Z. Phys. C52 (1991) 175
The average beam spot position was calculated as described in: OPAL Coll., P. Acton et al.:Phys. Lett. B274 (1992) 513
OPAL Coll., M. Z. Akrawy et al.: Z. Phys. C49 (1991) 375; JADE Colll., S. Bethke et al.: Phys. Lett. B213 (1988) 235; JADE Coll W Bartel et al.: Z. Phys. C 33 (1986) 23
T. Sjöstrand: Comput. Phys. Commun. 39 (1986)373. The parameters were tuned to OPAL data as described in: OPAL Coll., M.Z. Akrawy et al.: Z. Phys. C47 (1990) 505
J. Allison et al.: Nucl. Instrum. Methods A 317 (1992) 47
C. Peterson, D. Schlatter, I. Schmitt, P. Zerwas: Phys. Rev. D. 27 (1983) 105
Average and uncertainty on <x e>c and <x e>b dereived from combining the following pubslihed data: DELPHI Coll., P. Abreu et al.: Z. Phys. C 56 (1992) 47; L3 Coll., B. Adeva et al., Phys. Lett. B 271 (1991) 461; ALEPH Coll., D. Decamp et al.: Phys. Lett. B 266 (1991) 218; OPAL Coll., M.Z. Akrawy et al.: Phys. Lett. B 263 (1991) 311; OPAL Coll., G. Alexander et al.: Phys. Lett. B 262 (1991) 341; ALEPH Coll., D. Decamp et al.: Phys. Lett. B 244 (1990) 551
G. Altarelli et al.: Nucl. Phys. B 264 (1991) 219. The parameers of this model were taken to bep F=282 MeV/c andm s=50 MeV/c2 from a fit described in: CLEO Coll., S. Henderson et al.: Phys. Rev. D 45 (1992) 2212; M. Worris: CLNS Thesis 91-05, Cornell University, 1991, to DELCO data: DELCO Coll., W. Bacino et al.: Phys. Rev. Lett. 43 (1979) 1073
Particle Data Group, K. Hikasa et al.: Phys. Rev. D45 (1992) 1
Standard Model prediction from ZF IT TFR forM Z o=91.175 GeV/c2,M top=140 GeV/c2,M Higgs=300 GeV/c2 and\(\alpha _s (M_{Z^0 }^2 ) = 0.12\). D. Bardin et al.: CERN-TH.6443/92
OPAL Coll., G. Alexander et al.: Phys. Lett. B262 (1991) 341
B. Schumm, Y. Dokshitzer, V. Khoze, D. Koetke: Phys. Rev. Lett. 69 (1992) 3025
OPAL Coll., P. Acton et al.: Z. Phys. C53 (1992) 539
OPAL Coll., G. Alexander et al.: Phys. Lett. B264 (1991) 467
OPAL Coll., P. Acton et al.: Z. Phys. C60 (1993) 217
OPAL Coll., P. Acton et al.: Z. Phys. C60 (1993) 19
N. Isgur, D. Scora, B. Grinstein, M. Wise: Phys. Rev. D 45 (1989) 799
L. Lyons, D. Gibaut, P. Clifford: Nucl. Instrum. Methods A 270 (1988) 110
Author information
Authors and Affiliations
Consortia
Rights and permissions
About this article
Cite this article
OPAL Collaboration., Akers, R., Alexander, G. et al. Measurement of\(\Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)\) using impact parameters and leptons. Z. Phys. C - Particles and Fields 61, 357–369 (1994). https://doi.org/10.1007/BF01413175
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01413175