14187092
Inclusive semileptonic branching ratios of b hadrons produced in Z decays
A measurement of the inclusive semileptonic branching ratios of b hadrons produced in Z decay is presented, using four million hadronic events collected by the ALEPH detector from 1991 to 1995. Electrons and muons are selected opposite to b-tagged hemispheres. Two different methods are explored to distinguish the contributions from direct $\bl$ and cascade $\bcl$ dec ays to the total lepton yield. One is based on the lepton transverse momentum spectrum, the other makes use of the correlation between the charge of the lepton and charge estimators built from tracks in the opposite hemisphere of the event. The latter method reduces the dependence on the modelling of semileptonic b decays. The results obtained by averaging the two techniques are BR(b->l) = 0.1070 +- 0.0010 +- 0.0023 +- 0.0026 BR(b->c->l) = 0.0818 +- 0.0015 +- 0.0022 + 0.0022 -0.0014
123148086
Charm counting in b decays
The inclusive production of charmed particles in decays has been measured from the yield of D0, D+, Ds+ and Λc+ decays in a sample of events with high b purity collected with the ALEPH detector from 1992 to 1995. From these measurements, adding the charmonia production rate and an estimate of the charmed strange baryon contribution, the average number of charm quarks per b decay is determined to be nc = 1.230 ± 0.036 ± 0.038 ± 0.053, where the uncertainties are due to statistics, systematic effects and branching ratios, respectively.
15227858
Measurement of W pair production in e+ e- collisions at 183-GeV
Abstract The production of W + W − pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb −1 . Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57±0.62 (stat.) ±0.29 (syst.) pb . Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W→hadrons) =68.93±1.21 (stat.) ±0.51 (syst.) % , allowing a determination of the CKM matrix element |V cs |=1.043±0.058 (stat.) ±0.026 (syst.) . The agreement of the cross sections with the Standard Model prediction allows a limit to be set on the W decay rate to undetectable final states.
53511895
Measurement of the W mass in $e^+e^-$ collisions at production threshold
In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e+e− collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb−1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be σWW = 4.23 ± 0.73 (stat.) ± 0.19 (syst.) pb. From this cross-section, the W mass is derived within the framework of the Standard Model: mW = 80.14 ± 0.34 (stat.) ± 0.09 (syst.) ± 0.03 (LEP energy) GeV/c2
144007210
A precise determination of the number of families with light neutrinos and of the Z boson partial widths
More extensive and precise results are reported on the parameters of Z decay. On the basis of 20 000 Z decays collected with the ALEPH detector at LEP we find Mz=91.182±0.026 (exp.) ±0.030 (beam) GeV, Γz=2.541±0.056 GeV and σhad0=41.4±0.8 nb. The partial widths for the hadronic and leptonic channels are Γhad=1804±44 MeV, Γe+e−=82.1±3.4 MeV, Γμ+μ−=87.9±6.0 MeV and Γτ+τ−=86.1±5.6 MeV, in good agreement with the standard model. On the basis of the average leptonic width Γl+l−=83.9±2.2 MeV, the effective weak mixing angle is found to be sin2θw(Mz)=0.231±0.008. Usin g the partial widths calculated in the standard model, the number of light neutrino families is Nν=3.01±0.15 (exp.)±0.05 (theor.).
91183149
Measurement of the tau lepton lifetime
The mean lifetime of the lepton is measured in a sample of 25700 pairs collected in 1992 with the ALEPH detector at LEP. A new analysis of the 1-1 topology events is introduced. In this analysis, the dependence of the impact parameter sum distribution on the daughter track momenta is taken into account, yielding improved precision compared to other impact parameter sum methods. Three other analyses of the oneand three-prong decays are updated with increased statistics. The measured lifetime is 293:5 3:1 1:7 fs. Including previous (1989{1991) ALEPH measurements, the combined lifetime is 293:7 2:7 1:6 fs. (Submitted to Physics Letters B) See the following pages for the list of authors. The ALEPH Collaboration D. Buskulic, D. Casper, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J.-P. Lees, A. Lucotte, M.-N. Minard, P. Odier, B. Pietrzyk Laboratoire de Physique des Particules (LAPP), INP-CNRS, 74019 Annecy-le-Vieux Cedex, France F. Ariztizabal, M. Chmeissani, J.M. Crespo, I. Efthymiopoulos, E. Fernandez, M. Fernandez-Bosman, V. Gaitan, Ll. Garrido, M. Martinez, S. Orteu, A. Pacheco, C. Padilla, F. Palla, A. Pascual, J.A. Perlas, F. Sanchez, F. Teubert Institut de Fisica d'Altes Energies, Universitat Autonoma de Barcelona, 08193 Bellaterra (Barcelona), Spain A. Colaleo, D. Creanza, M. de Palma, A. Farilla, G. Gelao, M. Girone, G. Iaselli, G. Maggi, M. Maggi, N. Marinelli, S. Natali, S. Nuzzo, A. Ranieri, G. Raso, F. Romano, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, G. Zito Dipartimento di Fisica, INFN Sezione di Bari, 70126 Bari, Italy X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao Institute of High-Energy Physics, Academia Sinica, Beijing, The People's Republic of China G. Bonvicini, M. Cattaneo, P. Comas, P. Coyle, H. Drevermann, A. Engelhardt, R.W. Forty, M. Frank, R. Hagelberg, J. Harvey, R. Jacobsen, P. Janot, B. Jost, E. Kneringer, J. Knobloch, I. Lehraus, C. Markou, E.B. Martin, P. Mato, A. Minten, R. Miquel, T. Oest, P. Palazzi, J.R. Pater, J.F. Pusztaszeri, F. Ranjard, P. Rensing, L. Rolandi, D. Schlatter, M. Schmelling, O. Schneider, W. Tejessy, I.R. Tomalin, A. Venturi, H. Wachsmuth, W. Wiedenmann, T. Wildish, W. Witzeling, J. Wotschack European Laboratory for Particle Physics (CERN), 1211 Geneva 23, Switzerland Z. Ajaltouni, M. Bardadin-Otwinowska, A. Barres, C. Boyer, A. Falvard, P. Gay, C. Guicheney, P. Henrard, J. Jousset, B. Michel, S. Monteil, J-C. Montret, D. Pallin, P. Perret, F. Podlyski, J. Proriol, J.-M. Rossignol, F. Saadi Laboratoire de Physique Corpusculaire, Universit e Blaise Pascal, INP-CNRS, Clermont-Ferrand, 63177 Aubi ere, France T. Fearnley, J.B. Hansen, J.D. Hansen, J.R. Hansen, P.H. Hansen, B.S. Nilsson Niels Bohr Institute, 2100 Copenhagen, Denmark A. Kyriakis, E. Simopoulou, I. Siotis, A. Vayaki, K. Zachariadou Nuclear Research Center Demokritos (NRCD), Athens, Greece A. Blondel, G. Bonneaud, J.C. Brient, P. Bourdon, L. Passalacqua, A. Roug e, M. Rumpf, R. Tanaka, A. Valassi, M. Verderi, H. Videau Laboratoire de Physique Nucl eaire et des Hautes Energies, Ecole Polytechnique, INP-CNRS, 91128 Palaiseau Cedex, France D.J. Candlin, M.I. Parsons Department of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom E. Focardi, G. Parrini Dipartimento di Fisica, Universit a di Firenze, INFN Sezione di Firenze, 50125 Firenze, Italy M. Corden, M. Del no, C. Georgiopoulos, D.E. Ja e Supercomputer Computations Research Institute, Florida State University, Tallahassee, FL 323064052, USA 13;14 A. Antonelli, G. Bencivenni, G. Bologna, F. Bossi, P. Campana, G. Capon, V. Chiarella, G. Felici, P. Laurelli, G. Mannocchi, F. Murtas, G.P. Murtas, M. Pepe-Altarelli Laboratori Nazionali dell'INFN (LNF-INFN), 00044 Frascati, Italy S.J. Dorris, A.W. Halley, I. ten Have, I.G. Knowles, J.G. Lynch, W.T. Morton, V. O'Shea, C. Raine, P. Reeves, J.M. Scarr, K. Smith, M.G. Smith, A.S. Thompson, F. Thomson, S. Thorn, R.M. Turnbull Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ,United Kingdom U. Becker, O. Braun, C. Geweniger, G. Graefe, P. Hanke, V. Hepp, E.E. Kluge, A. Putzer, B. Rensch, M. Schmidt, J. Sommer, H. Stenzel, K. Tittel, S. Werner, M. Wunsch Institut f ur Hochenergiephysik, Universitat Heidelberg, 69120 Heidelberg, Fed. Rep. of Germany R. Beuselinck, D.M. Binnie, W. Cameron, D.J. Colling, P.J. Dornan, N. Konstantinidis, L. Moneta, A. Moutoussi, J. Nash, G. San Martin, J.K. Sedgbeer, A.M. Stacey Department of Physics, Imperial College, London SW7 2BZ, United Kingdom G. Dissertori, P. Girtler, D. Kuhn, G. Rudolph Institut f ur Experimentalphysik, Universitat Innsbruck, 6020 Innsbruck, Austria C.K. Bowdery, T.J. Brodbeck, P. Colrain, G. Crawford, A.J. Finch, F. Foster, G. Hughes, T. Sloan, E.P. Whelan, M.I. Williams Department of Physics, University of Lancaster, Lancaster LA1 4YB, United Kingdom A. Galla, A.M. Greene, K. Kleinknecht, G. Quast, J. Raab, B. Renk, H.-G. Sander, R. Wanke, P. van Gemmeren C. Zeitnitz Institut f ur Physik, Universitat Mainz, 55099 Mainz, Fed. Rep. of Germany J.J. Aubert, A.M. Bencheikh, C. Benchouk, A. Bonissent, G. Bujosa, D. Calvet, J. Carr, C. Diaconu, F. Etienne, M. Thulasidas, D. Nicod, P. Payre, D. Rousseau, M. Talby Centre de Physique des Particules, Facult e des Sciences de Luminy, INP-CNRS, 13288 Marseille, France I. Abt, R. Assmann, C. Bauer, W. Blum, D. Brown, H. Dietl, F. Dydak, G. Ganis, C. Gotzhein, K. Jakobs, H. Kroha, G. L utjens, G. Lutz, W. M anner, H.-G. Moser, R. Richter, A. Rosado-Schlosser, S. Schael, R. Settles, H. Seywerd, R. St. Denis, G. Wolf Max-Planck-Institut f ur Physik, Werner-Heisenberg-Institut, 80805 M unchen, Fed. Rep. of Germany R. Alemany, J. Boucrot, O. Callot, A. Cordier, F. Courault, M. Davier, L. Du ot, J.-F. Grivaz, Ph. Heusse, M. Jacquet, D.W. Kim, F. Le Diberder, J. Lefran cois, A.-M. Lutz, G. Musolino, I. Nikolic, H.J. Park, I.C. Park, M.-H. Schune, S. Simion, J.-J. Veillet, I. Videau Laboratoire de l'Acc el erateur Lin eaire, Universit e de Paris-Sud, INP-CNRS, 91405 Orsay Cedex, France D. Abbaneo, P. Azzurri, G. Bagliesi, G. Batignani, S. Bettarini, C. Bozzi, G. Calderini, M. Carpinelli, M.A. Ciocci, V. Ciulli, R. Dell'Orso, R. Fantechi, I. Ferrante, F. Fidecaro, L. Fo a, F. Forti, A. Giassi, M.A. Giorgi, A. Gregorio, F. Ligabue, A. Lusiani, P.S. Marrocchesi, A. Messineo, G. Rizzo, G. Sanguinetti, A. Sciab a, P. Spagnolo, J. Steinberger, R. Tenchini, G. Tonelli, G. Triggiani, C. Vannini, P.G. Verdini, J. Walsh Dipartimento di Fisica dell'Universit a, INFN Sezione di Pisa, e Scuola Normale Superiore, 56010 Pisa, Italy A.P. Betteridge, G.A. Blair, L.M. Bryant, F. Cerutti, Y. Gao, M.G. Green, D.L. Johnson, T. Medcalf, Ll.M. Mir, P. Perrodo, J.A. Strong Department of Physics, Royal Holloway & Bedford New College, University of London, Surrey TW20 OEX, United Kingdom V. Bertin, D.R. Botterill, R.W. Cli t, T.R. Edgecock, S. Haywood, M. Edwards, P. Maley, P.R. Norton, J.C. Thompson Particle Physics Dept., Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX, United Kingdom B. Bloch-Devaux, P. Colas, S. Emery, W. Kozanecki, E. Lan con, M.C. Lemaire, E. Locci, B. Marx, P. Perez, J. Rander, J.-F. Renardy, A. Roussarie, J.-P. Schuller, J. Schwindling, A. Trabelsi, B. Vallage CEA, DAPNIA/Service de Physique des Particules, CE-Saclay, 91191 Gif-sur-Yvette Cedex, France R.P. Johnson, H.Y. Kim, A.M. Litke, M.A. McNeil, G. Taylor Institute for Particle Physics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA A. Beddall, C.N. Booth, R. Boswell, S. Cartwright, F. Combley, I. Dawson, A. Koksal, M. Letho, W.M. Newton, C. Rankin, L.F. Thompson Department of Physics, University of She eld, She eld S3 7RH, United Kingdom A. Bohrer, S. Brandt, G. Cowan, E. Feigl, C. Grupen, G. Lutters, J. Minguet-Rodriguez, F. Rivera, P. Saraiva, L. Smolik, F. Stephan, Fachbereich Physik, Universitat Siegen, 57068 Siegen, Fed. Rep. of Germany M. Apollonio, L. Bosisio, R. Della Marina, G. Giannini, B. Gobbo, F. Ragusa Dipartimento di Fisica, Universit a di Trieste e INFN Sezione di Trieste, 34127 Trieste, Italy J. Rothberg, S. Wasserbaech Experimental Elementary Particle Physics, University of Washington, WA 98195 Seattle, U.S.A. S.R. Armstrong, L. Bellantoni, P. Elmer, Z. Feng, D.P.S. Ferguson, Y.S. Gao, S. Gonz alez, J. Grahl, J.L. Harton, O.J. Hayes, H. Hu, P.A. McNamara III, J.M. Nachtman, W. Orejudos, Y.B. Pan, Y. Saadi, M. Schmitt, I.J. Scott, V. Sharma, J.D. Turk, A.M. Walsh, Sau Lan Wu, X. Wu, J.M. Yamartino, M. Zheng, G. Zobernig Department of Physics, University of Wisconsin, Madison, WI 53706, USA Now at CERN, 1211 Geneva 23, Switzerland. Deceased. Now at Dipartimento di Fisica, Universit a di Lecce, 73100 Lecce, Italy. Also Istituto di Fisica Generale, Universit a di Torino, Torino, Italy. Also Istituto di Cosmo-Geo sica del C.N.R., Torino, Italy. Supported by the Commission of the European Communities, contract ERBCHBICT941234. Supported by CICYT, Spain. Supported by the National Science Foundation of China. Supported by the Danish Natural Science Research Council. Supported by the UK Particle Physics and Astronomy Research Council. Supported by the US Department of Energy, grant DE-FG0295-ER40896. On leave from Universitat Autonoma de Barcelona, Barcelona, Spain. Supported by the US Department of Energy, contract DE-FG05-92ER40742. Supported by the US Department of Energy, contract DE-FC05-85ER250000. Permanent address: Universitat de Barcelona, 08208 Barcelona, Spain. Supported by the Bundesministerium f ur Forschung und Technologie, Fed. Rep. of Germany. Supported by the Direction des Sciences de la Mati ere, C.E.A. Supported by Fonds zur F orderung der wissenschaftlichen Forschung, Austria. Permanent address: Kangnung National University, Kangnung, Korea. Now at Dipartimento di Fisica, Universit a di Milano, Milano, Italy. Also at CERN, 1211 Geneva 23, Switzerland. Supported by the US Department of Energy, grant DE-FG0
118141327
Hurst parameter analysis of radio pulsar timing noise
We present an analysis of timing residual (noise) of 54 pulsars obtained from 25-m radio telescope at Urumqi Observatory with a time span of 5~8 years, dealing with statistics of the Hurst parameter. The majority of these pulsars were selected to have timing noise that look like white noise rather than smooth curves. The results are compared with artificial series of different constant pairwise covariances. Despite the noise like appearance, many timing residual series showed Hurst parameters significantly deviated from that of independent series. We concluded that Hurst parameter may be capable of detecting dependence in timing residual and of distinguishing chaotic behavior from random processes.
119244576
The optical/UV excess of isolated neutron stars in the RCS model
The X-ray dim isolated neutron stars (XDINSs) are peculiar p ulsar-like objects, characterized by their very well Planck-like spectrum. In s tudying their spectral energy distributions, the optical/UV excess is a long standing pro blem. Recently, Kaplan et al. (2011) have measured the optical/UV excess for all seven sou rces, which is understandable in the resonant cyclotron scattering (RCS) model previ ously addressed. The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources . The flat spectrum of RX J2143.0+0654 may due to contribution from bremsstrahlung emission of the electron system in addi tion to the RCS process.
9804601
Measurement of the inclusive decay properties of charmed mesons
Abstract We report a high statistics study of the inclusive decay properties of the charmed D 0 and D + mesons, and the first inclusive study of the charmed D s + . The data are collected at s =3.77 GeV and s =4.14 GeV with the Mark III detector at the e + e − storage ring SPEAR. For each charmed meson species, the charged-particle multiplicity, the strangeness content of the final state, and the average π 0 multiplicity are determined.
119021615
Can the Age Discrepancies of Neutron Stars Be Circumvented by an Accretion-assisted Torque?
It is found that 1E 1207.4-5209 could be a low-mass bare strange star if its small radius or low-altitude cyclotron formation can be identified. The age problems of five sources could be solved by a fossil-disk-assisted torque. The magnetic dipole radiation dominates the evolution of PSR B1757-24 at present, and the others are in propeller (or tracking) phases.
118446912
Radio and gamma-ray emission from pulsars
The radiation of pulsars have been observed for many years. A few pulsars are discovered to have both radio and gamma-ray emission. Many models on pulsar radiation have been developed, but so far we are still lacking an elaborate model which can explain the emission from radio to gamma-rays in detail. In this paper we present a joint model for radio and gamma-ray emission, in which both the dominate emission mechanisms are inverse Compton scattering. The pulse profiles at radio and gamma-ray bands are reproduced for the Crab-like, Vela-like and Geminga-like pulsars, in good agreement with observations.