The HARP Time Projection Chamber: Characteristics and Physics Performance

The HARP spectrometer that took data at the CERN Proton Synchrotron in 2001 and 2002 had as large-angle detector system a Time Projection Chamber (TPC) surrounded by Resistive Plate Chambers. The design of the TPC, experience with its operation, and its good physics performance are described. The successful recovery from track distortions arising from inhomogeneities of the electric and magnetic fields in the TPC volume is discussed

Measurement of prompt photon production in hadronic Z decays

The production of isolated photons in hadronicZ decays is measured with the ALEPH detector at LEP using a sample of 450 000 hadronic events. The corrected rate is given for several values of the minimum invariant mass squared cut between the photon and the jets. This measurement of final state radiation from the quarks is compared with the predictions of parton shower models JETSET, ARIADNE and HERWIG as well as with the predictions of QCD matrix element calculations

MEASUREMENT OF PROMPT PHOTON PRODUCTION IN HADRONIC-Z DECAYS

The production of isolated photons in hadronic Z decays is measured with the ALEPH detector at LEP using a sample of 450 000 hadronic events. The corrected rate is given for several values of the minimum invariant mass squared cut between the photon and the jets. This measurement of final state radiation from the quarks is compared with the predictions of parton shower models JETSET, ARIADNE and HERWIG as well as with the predictions of QCD matrix element calculations

Properties of hadronic Z decays and test of QCD generators

Distributions are presented of event shape variables, jet roduction rates and charged particle momenta obtained from 53 000 hadronicZ decays. They are compared to the predictions of the QCD+hadronization models JETSET, ARIADNE and HERWIG, and are used to optimize several model parameters. The JETSET and ARIADNE coherent parton shower (PS) models with running αs and string fragmentation yield the best description of the data. The HERWIG parton shower model with cluster fragmentation fits the data less well. The data are in better agreement with JETSET PS than with JETSETO(αS2) matrix elements (ME) even when the renormalization scale is optimized