A Measurement of the average bottom hadron lifetime

The average b hadron lifetime, тb, has been measured using approximately 3.5 million hadronic events collected with the OPAL detector at LEP between 1991 and 1994. A lifetime tag based_ on a neural network algorithm was used to select Z0 → bb events. A secondary vertex reconstructed on the opposite side from the b-tag was used to measure the b hadron decay length. This was combined with an estimate of the b hadron momentum, allowing the b hadron decay time to be evaluated. The lifetime, тb = 1.611 ± 0.010 (stat) ± 0.027 (syst) ps, was extracted from a fit involving the distribution of the 95620 decay times reconstructed in the data and the corresponding distribution in Monte Carlo.

electron positron: colliding beams
electron positron: annihilation
Z0: electroproduction
Z0: hadronic decay
bottom: pair production
bottom particle: lifetime
bottom particle: decay
bottom particle: momentum
track data analysis: vertex
neural network

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