Philip Burrows

Abstract:

The structure of e+e-→bb̄g events was studied using Z0 decays recorded in the SLC Large Detector experiment at SLAC. Three-jet final states were selected and the charge-coupled device-based vertex detector was used to identify two of the jets as b or b. Distributions of the gluon energy and polar angle were measured over the full kinematic range for the first time, and compared with perturbative QCD predictions. The energy distribution is potentially sensitive to an anomalous b chromomagnetic moment κ. We measured κ to be consistent with zero and set the first limits on its value: -0.17<κ<0.11 at 95% C.L. ©1999 The American Physical Society.

Abstract:

We have measured the differential production cross sections as a function of scaled momentum xp=2p/Ec.m. of the identified hadron species π⁺, K⁺, K⁰, K*⁰, φ, p, Λ⁰, and of the corresponding antihadron species in inclusive hadronic Z⁰ decays, as well as separately for Z⁰ decays into light (u, d, s), c and b flavors. Clear flavor dependences are observed, consistent with expectations based upon previously measured production and decay properties of heavy hadrons. These results were used to test the QCD predictions of Gribov and Lipatov, the predictions of QCD in the modified leading logarithm approximation with the ansatz of local parton-hadron duality, and the predictions of three fragmentation models. The ratios of production of different hadron species were also measured as a function of xp and were used to study the suppression of strange meson, strange and non-strange baryon, and vector meson production in the jet fragmentation process. The light-flavor results provide improved tests of the above predictions, as they remove the contribution of heavy hadron production and decay from that of the rest of the fragmentation process. In addition we have compared hadron and antihadron production as a function of xp in light quark (as opposed to antiquark) jets. Differences are observed at high xp, providing direct evidence that higher-momentum hadrons are more likely to contain a primary quark or antiquark. The differences for pseudoscalar and vector kaons provide new measurements of strangeness suppression for high-xp fragmentation products. ©1999 The American Physical Society.

Abstract:

We present a direct measurement of the parity-violating asymmetry Ab in the Z⁰ to bb̄ coupling using a new technique to distinguish the b and b̄ quarks using charged kaons from B decays. The Z⁰ bosons are produced in e⁺ē collisions at the SLC with longitudinally polarized electrons. bb̄ events are selected using a secondary vertex mass tag and Ab is determined from the left-right forward-backward asymmetry. From the 1994–1995 data sample, selected from 100 000 hadronic Z⁰ decays, we obtain Ab = 0.855 ± 0.088stat ± 0.102syst. © 1999 The American Physical Society.

Abstract:

We present an improved comparison of the strong coupling of the gluon to light [Formula Presented] c, and b quarks, determined from multijet rates in flavor-tagged samples of hadronic [Formula Presented] decays recorded with the SLC Large Detector at the SLAC Linear Collider between 1993 and 1995. Flavor separation among primary [Formula Presented] [Formula Presented] and [Formula Presented] final states was made on the basis of the reconstructed mass of long-lived heavy-hadron decay vertices, yielding tags with high purity and low bias against ⩾ 3-jet final states. We find: [Formula Presented] and [Formula Presented] © 1998 The American Physical Society.

Abstract:

We have studied the determination of the running b-quark mass, mb(MZ), using Z⁰ decays into 3 or more hadronic jets. We calculated the ratio of ≥ 3-jet fractions in e⁺e^- → bb̄ versus e^-e^- qlq̄l (q^l = u or d or s) events at next-to-leading order in perturbative QCD using six different infra-red- and collinear-safe jet-finding algorithms. We compared with corresponding measurements from the SLD Collaboration and found a significant algorithm-dependence of the fitted m^b(MZ) value. Our best estimate, taking correlations into account, is mb(MZ) = 2.56 ± 0.27 (stat.) -0.38^+0.28 (syst.) -1.48^+0.49 (theor.) GeV/c². © 1999 Published by Elsevier Science B.V. All rights reserved.