F.F. Heymann

The Detector simulation program for the OPAL experiment at LEP

The Monte Carlo program for the OPAL experiment at the LEP ee collider is described. This program is based on the GEANT simulation package. The general organization of the program is outlined, and a description is given of the techniques used for simulating the various subdetectors of OPAL. The performance of the program is illustrated by comparisons with recent data recorded by OPAL at LEP. (Submitted to Nucl. Instr. and Meth.) School of Physics and Space Research, University of Birmingham, Birmingham, B15 2TT, UK Dipartimento di Fisica dell Universit a di Bologna and INFN, Bologna, 40126, Italy CNAF-INFN, Bologna, Italy Physikalisches Institut, Universitx7fat Bonn, D-5300 Bonn 1, FRG Department of Physics, University of California, Riverside, CA 92521 USA Cavendish Laboratory, Cambridge, CB3 0HE, UK Carleton University, Dept of Physics, Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada Centre for Research in Particle Physics, Carleton University, Ottawa, Ontario K1S 5B6, Canada CERN, European Organisation for Particle Physics, 1211 Geneva 23, Switzerland Enrico Fermi Institute and Department of Physics, University of Chicago, Chicago Illinois 60637, USA Fakultx7f at fx7f ur Physik, Albert Ludwigs Universitx7fat, D-7800 Freiburg, FRG Universitx7fat Hamburg/DESY, II Inst. fx7f ur Experimental Physik, 2000 Hamburg 52, FRG Physikalisches Institut, Universitx7fat Heidelberg, Heidelberg, FRG Queen Mary and West eld College, University of London, London, E1 4NS, UK University College London, London, WC1E 6BT, UK Department of Physics, Schuster Laboratory, The University, Manchester, M13 9PL, UK Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742, USA Laboratoire de Physique Nucl eaire, Universit e de Montr eal, Montr eal, Quebec, H3C 3J7, Canada Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK DPhPE, CEN Saclay, F-91191 Gif-sur-Yvette, France International Centre for Elementary Particle Physics, University of Tokyo, Tokyo 113, Japan Brunel University, Uxbridge, Middlesex, UB8 3PH UK Nuclear Physics Department, Weizmann Institute of Science, Rehovot, 76100, Israel Present address: EPFL, Lausanne, Switzerland Present address: Applied Silicon Inc, Ottawa, Canada Present address: Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK On leave from Birmingham University, Birmingham B15 2TT, UK Present address: Culham Laboratory, Culham, Oxfordshire, UK Present address: Meiji Gakuin University, Yokohama 244, Japan

Production spectra of π±, K±, p± at large angles in proton-proton collisions in the CERN intersecting storage rings

Abstract Results are given on the inclusive production of charged pions, kaons, and nucleons, in proton-proton collisions at c.m. energies from √ s = 23 to 63 GeV at large angles and for the transverse momentum range 0.1 p T c . The dependence of the production spectra on the collision energy √ s , the transverse momentum p T , and the longitudinal rapidity is discussed.

Production of high transverse momentum particles in p-p-collisions in the central region at the CERN ISR

Abstract The inclusive production al all charged particles of transverse momentum p T between 1.5 and 4.4 GeV/ c at centre of mass angles 90° and 59.4° from p-p-collisions with √ s = 44 and 53 GeV has been measured. No strong energy dependence is observed for these transverse momenta.

Direct observation of the decay of beauty particles into charm particles

Abstract The associated production of a pair of beauty particles B− and B 0 by a 350 GeV π− interaction has been observed in an emulsion target inserted in an array of silicon microstrip detectors. Both beauty particles decay into charm particles, both of which are also observed to decay in the emulsion. Two negative muons were identified and their momenta measured in a large muon spectrometer. One muon has a pT of 1.9 GeV/c and is associated with a beauty particle decay. The other, with a pT of 0.45 GeV/c is associated with a charm particle decay. The flight times of the two beauty particles are respectively (0.8 ± 0.1) × 10−13 s and (5+2−1) × 10−13 s. Alternative interpretations of this event have negligible probability.

Large angle production of stable particles heavier than the proton and a search for quarks at the CERN intersecting storage rings

Abstract Measurements have been performed on production of particles with mass 1.5 GeV/c2 and charge ⩾ 2 3 for θlab = 62.5° and s = 53 GeV . At pT = 0.7 GeV/c the relative rate of production of antideuterons to π− is (5 ± 1) × 10−5. The deuteron to antideuteron ratio is 3.7 ± 1.2. No new stable particle has been amongst 0.7 × 108 charged particles entering our detector.

Large-angle inclusive production of charged pions at the CERN ISR with transverse moment a less than 1.0 GeV/c

Abstract The inclusive production of π ± in proton-proton collisons has been measured for the transverse momentum range 0.15 to 1.0 GeV/ c over an angular range of 29° to 89° in the centre-of-mass system and for centre-of-mass energies √ s = 30.6 and 52.8 GeV. For each energy the invariant cross-section foe fixed transverse momentum was found to increase by about 15% as the centre-of-mass rapidity decreases from 1 to 0, i.e. the “central plateau” has not yet been reached.

Large-angle inclusive production of protons, antiprotons and kaons, and particle composition at the CERN ISR

The production cross-sections for protons, antiprotons and kaons in proton-proton collisions at centre-of-mass energies s=30.6 and 52.8 GeV at large angles and for the transverse momentum range pT<1.2 GeV/c for protons and antiprotons and 0.2<pT<0.5 GeV/c for kaons have been measured. The charged particle composition is given in the range 0.2<pT<0.5 GeV/c and show that the K± and p± components have doubled over this pT-range. The ratio of positive to negative produced particles increases with pT.

THE DOUBLE ASSOCIATED PRODUCTION OF CHARMED PARTICLES BY THE INTERACTION OF 350 GEV/C PI-MESONS WITH EMULSION NUCLEI

Abstract Evidence is reported for the simultaneous production of four charmed particles in interactions induced by 350 GeV/ c π − mesons in stacks of nuclear emulsions. The events were found during a search for beauty particles among a sample of about 200 interactions with candidates for charmed particles. The events selected required the presence of at least one muon with a high component of momentum transverse to the beam direction.

The production of beauty particles in π−-U interactions at 320 GeV energy

Abstract B B production in π − -uranium interactions has been observed at 320 GeV beam energy looking at events with three muons in the final state. The cross section is found to be σ B B = 4.5±1.4±1.4 nb per nucleon (for a linear A -dependence) or σ B B = 17.6±5.5±5.5 nb per nucleon (assuming A 0.75 dependence). An estimate of x F distribution is given.

A Hybrid Experiment to Search for Beauty Particles

We give here a detailed description of experiment WA75, which was performed at CERN to search for beauty particles. Events containing at least one muon with a high momentum transverse to the beam direction were selected; then the primary interactions and decay vertices, located in stacks of nuclear research emulsions, were examined and analysed. The various parts of the apparatus are described and the off-line analysis and search in emulsion are discussed. An estimate is made of the sensitivity of the experiment to beauty- and charmed-particle production.