A measurement of the partial width ratio GAMMA(bbBAR)/GAMMA(had) using a method which tags the Z --> bbBAR decays through the lifetime 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 GAMMA(bbBAR)/GAMMA(had) 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 GAMMA(bbBAR)/GAMMA(had) = 0.2192+/-0.0022(stat.)+/-0.0026(syst.)+/-0.0016(GAMMA(ccBAR)/GAMMA(had)) is found. Combining this result with other recent ALEPH GAMMA(bbBAR)/GAMMA(had) measurements gives a 95% confidence upper limit on the Standard Model top mass of M(t) < 228 GeV. RI ANTONELLI, ANTONELLA/C-6238-2011; Buttar, Craig/D-3706-2011; Stahl, Achim/E-8846-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012
A PRECISE MEASUREMENT OF GAMMA-Z-]B(B)BAR/GAMMA-Z-] HADRONS
ROLANDI, LUIGI;LIGABUE, FRANCO;LUSIANI, Alberto;
1993-01-01
Abstract
A measurement of the partial width ratio GAMMA(bbBAR)/GAMMA(had) using a method which tags the Z --> bbBAR decays through the lifetime 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 GAMMA(bbBAR)/GAMMA(had) 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 GAMMA(bbBAR)/GAMMA(had) = 0.2192+/-0.0022(stat.)+/-0.0026(syst.)+/-0.0016(GAMMA(ccBAR)/GAMMA(had)) is found. Combining this result with other recent ALEPH GAMMA(bbBAR)/GAMMA(had) measurements gives a 95% confidence upper limit on the Standard Model top mass of M(t) < 228 GeV. RI ANTONELLI, ANTONELLA/C-6238-2011; Buttar, Craig/D-3706-2011; Stahl, Achim/E-8846-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
