121527337
A Study of single $W$ production in $e^+ e^-$ collisions at $S^(1/2)$ = 161-GeV to 183-GeV
Abstract Single W production is studied in the data recorded with the ALEPH detector at LEP at centre-of-mass energies between 161 and 183 GeV. The cross section is measured to be σW=0.41±0.17(stat.)±0.04(syst.) pb at 183 GeV, consistent with the Standard Model expectation. Limits on non-standard WWγ couplings are deduced as −1.6 γ (λ γ =0) and −1.6 γ (κ γ =1) at 95% C.L. A search for effectively invisible decays of the W boson in W pair production is performed, leading to an upper limit on the branching ratio of 1.3% ( Γ inv =27 MeV ) at 95% C.L.
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
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.).
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.
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
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.
118630060
What can Fermi tell us about magnetars
We have analyzed the physical implications of Fermi observations of magnetars. Observationally, no significant detection is reported in Fermi observations of all magnetars. Then there are conflicts between outer gap model in the case of magnetars and Fermi observations. One possible explanation is that magnetars are wind braking instead of magnetic dipole braking. In the wind braking scenario, magnetars are neutron stars with strong multipole field. A strong dipole field is no longer required. A magnetism-powered pulsar wind nebula and a braking index smaller than three are the two predictions of wind braking of magnetars. Future deeper Fermi observations will help us make clear whether they are wind braking or magnetic dipole braking. It will also help us to distinguish between the magnetar model and the accretion model for AXPs and SGRs.
9662073
Effect of asymmetric strange–antistrange sea to the NuTeV anomaly
Abstract We calculate the strange quark and antiquark distributions of the nucleon by using the effective chiral quark model, and find that the strange–antistrange asymmetry can bring a contribution of about 60–100% to the NuTeV deviation of sin 2 θ w from the standard value measured in other electroweak processes. The results are insensitive to different inputs. The light-flavor quark asymmetry of d ¯ – u ¯ is also investigated and found to be consistent with the experimental measurements. Therefore the chiral quark model provides a successful picture to understand the NuTeV anomaly, as well as the light-flavor quark asymmetry and the proton spin problem in previous studies.
119215637
Alfven seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star
Magneto-solid-mechanical model of two-component, core-crust, paramagnetic neutron star responding to quake-induced perturbation by differentially rotational, torsional, oscillations of crustal electron-nuclear solid-state plasma about axis of magnetic field frozen in the immobile paramagnetic core is developed. Particular attention is given to the node-free torsional crust-against-core vibrations under combined action of Lorentz magnetic and Hooke's elastic forces; the damping is attributed to Newtonian force of shear viscose stresses in crustal solid-state plasma. The spectral formulas for the frequency and lifetime of this toroidal mode are derived in analytic form and discussed in the context of quasiperiodic oscillations of the x-ray outburst flux from quaking magnetars. The application of obtained theoretical spectra to modal analysis of available data on frequencies of oscillating outburst emission suggests that detected variability is the manifestation of crustal Alfven's seismic vibrations restored by Lorentz force of magnetic field stresses.
38831513
Nucleon sea in the effective chiral quark model
The asymmetries of both light-flavor antiquark d(x)-u(x) and strange-antistrange s(x)-s(x) distributions of the nucleon sea are considered with more details in the effective chiral quark model. We find that the asymmetric distribution of light-flavor antiquarks d(x)-u(x) matches the experimental data well and that the asymmetry of strange and antistrange distributions can bring about 60%-100% correction to the NuTeV anomaly of sin{sup 2}{theta}{sub w}, which are 3 standard deviations from the world average value measured in other electroweak processes. The results on the correction to the NuTeV anomaly are insensitive to the inputs of the constituent quark distributions and the cutoff parameters. The ratios of d(x)/u(x) and s(x)/s(x) are also discussed, and it is found that the ratio s(x)/s(x) is compatible with the available experiments with an additional symmetric sea contribution being considered effectively.
13183016
Strange quark stars - A review
A pedagogical overview of strange quark matter and strange stars is presented. After a historical notation of the research and an introduction to quark matter, a major part is devoted to the physics and astrophysics of strange stars, with attention being paid to the possible ways by which neutron stars and strange stars can be distinguished in astrophysics. Recent possible evidence for bare strange stars is also discussed.