Measurement of the average lifetime of b-hadrons in Z decays

• Published in: Physics letters. B 1998-01, Vol.416 (1), p.220-232
• Main Authors: Alcaraz, J, Alverson, G, Azemoon, T, Baksay, L, Banerjee, Sw, Baschirotto, A, Bilei, G.M, Böhm, A, Bourilkov, D, Burger, W.J, Castellini, G, Chen, M, Cifarelli, L, Clare, I, Degré, A, DeNotaristefani, F, DiBitonto, D, Dominguez, A, Duchesneau, D, Duinker, P, Duran, I, Ernenwein, J.P, Fabre, M, Faccini, R, Favara, A, Fernandez, D, Ferroni, F, Fiandrini, E, Fredj, L, Furetta, C, Ganguli, S.N, Garcia-Abia, P, Gau, S.S, Gentile, S, Gong, Z.F, Gupta, V.K, Hasan, A, Hebbeker, T, Hofer, H, Hong, S.J, Hou, S.R, Jones, L.W, de Jong, P, Kamyshkov, Yu, Karyotakis, Y, Kim, D, Kim, J.K, Kirkby, A, Koutsenko, V, Krenz, W, Lapoint, C, Laurikainen, P, Lecoq, P, Lin, W.T, Liu, Z.A, Lu, W, Malgeri, L, Maña, C, McNally, D, Moore, R, Napolitano, M, Nippe, A, Nowak, H, Organtini, G, Park, H.K, Patricelli, S, Perret-Gallix, D, Pevsner, A, Piccolo, D, Pieri, M, Pohl, M, Raven, G, Read, K, van Rhee, T, Rosier-Lees, S, Rosselet, Ph, Rubio, J.A, Schmidt-Kaerst, S, Schneegans, M, Scholz, N, Schwering, G, Smith, B, Straessner, A, Sun, L.Z, Susinno, G.F, Swain, J.D, Taylor, L, Ting, Samuel C.C, Tóth, J, Tully, C, Uwer, U, Van de Walle, R.T, Vesztergombi, G, Viertel, G, Vivargent, M, Ye, J.B, Zalite, An, Zhou, B, Zhou, Y, Zhu, R.Y
• Format: Article
• Language: English
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/S0370-2693(97)01379-8

We present a measurement of the average b-hadron lifetime τ b at the e +e − collider LEP. Using hadronic Z decays collected in the period from 1991 to 1994, two independent analyses have been performed. In the first one, the b-decay position is reconstructed as a secondary vertex of hadronic b-decay particles. The second analysis is an updated measurement of τ b using the impact parameter of leptons with high momentum and high transverse momentum. The combined result is τ b =[1549±9 (stat) ±15 (syst)] fs . In addition, we measure the average charged b-decay multiplicity 〈 n b〉 and the normalized average b-energy 〈 x E 〉 b at LEP to be 〈n b 〉=4.90±0.04 (stat)±0.11 (syst), 〈x E〉 b =0.709±0.004 (stat+syst).