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681.
Jets are collimated sprays of particles originating from fragmentation of high energy partons produced in a hard collision. They are an important diagnostic tool in studies of the Quark Gluon Plasma (QGP). The modification of the jet fragmentation pattern and its structure is a signature for the influence of hot and dense matter on the parton fragmentation process. Jet measurements in proton-proton collisions provide a baseline for similar measurements in heavy-ion collisions, while studies in proton-nucleus system allow to estimate cold nuclear matter effects. Here we present jet studies in different colliding systems (p–p, p–Pb, Pb–Pb) performed by the ALICE collaboration at LHC energies. Results on jet spectra, cross sections, nuclear modification factors, jet structure and other kinematic observables will be presented. 相似文献
682.
A. Breakstone R. Campanini H. B. Crawley G. M. Dallavalle M. M. Deninno K. Doroba D. Drijard F. Fabbri A. Firestone H. G. Fischer H. Frehse W. Geist G. Giacomelli R. Gokieli M. Gorbics P. Hanke M. Heiden W. Herr D. Isenhower E. E. Kluge J. W. Lamsa T. Lohse W. T. Meyer G. Mornacchi T. Nakada M. Panter A. Putzer K. Rauschnabel B. Rensch F. Rimondi M. Schmelling G. P. Siroli J. D. Skeens R. Sosnowski M. Szczekowski O. Ullaland D. Wegener R. Yeung Ames Collaboration Bologna Collaboration CERN Collaboration Dortmund Collaboration Heidelberg Collaboration Warsaw Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,43(3):522-522
Data are presented for the first time on inclusive Pomeron-Pomeron interactions which produce a central systemX (composed mainly of multimeson states) in proton-proton collisions at \(\sqrt s \) at the CERN ISR. The systemX has a Feynman-x distribution which is sharply peaked atx f=0, is inconsistent with any significant contributions from Reggeon exchange processes, and has an invariant mass dependence in good agreement with the predicted formM x ?2 . Kaon production is about 15% of pion production, nearly independent ofM x, while proton-antiproton production averages about 5% of pion production and increases withM x. The structure of the central systemX develops into a jetlike shape, asM x increases, as would be expected from a model of Pomeron fragmentation. The shape of thex f(π) distribution in the center of mass of theX system (although not proving existence) is consistent with asoft partonic substructure of the Pomeron. 相似文献
683.
Agakichiev G Appelshäuser H Baur R Bielcikova J Braun-Munzinger P Cherlin A Drees A Esumi SI Filimonov K Fraenkel Z Fuchs Ch Glässel P Hering G Huovinen P Lenkeit B Marín A Messer F Messer M Milosevic J Miśkowiec D Nix O Panebrattsev Y Petrácek V Pfeiffer A Rak J Ravinovich I Razin S Rehak P Sako H Saveljic N Schmitz W Shimansky S Socol E Specht HJ Stachel J Tilsner H Tserruya I Voigt C Voloshin S Weber C Wessels JP Wurm JP Yurevich V;CERES Collaboration 《Physical review letters》2004,92(3):032301
Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-p(T) pions (p(T)>1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb+Au collisions by the CERES experiment. Elliptic flow (v(2)) rises linearly with p(T) to a value of about 10% at 2 GeV/c. Beyond p(T) approximately 1.5 GeV/c, the slope decreases considerably, possibly indicating a saturation of v(2) at high p(T). Two-pion azimuthal anisotropies for p(T)>1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening. 相似文献
684.
685.
U. Gensch R. Klein H. J. Schreiber M. Walter H. Graessler D. Kuhn D. R. O. Morrison F. Triantis R. Barloutaud C. Cochet D. Denegri M. L. Faccini-Turluer A. Givernaud E. P. Kistenev A. A. Minaenko D. I. Patalakha E. Kozlovsky J. Macnaughton France-Soviet Union Collaboration CERN-Soviet Union Collaboration 《Zeitschrift fur Physik C Particles and Fields》1979,2(1):7-10
Antilambda production is studied inK ? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep ⊥ 2 distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK - p→Λ \(\bar \Lambda \) +X K - p→ \(\bar \Lambda \) K n +X, andK - p→ \(\bar \Lambda \) p+X. 相似文献
686.
J. Dorenbosch J. V. Allaby U. Amaldi G. Barbiellini F. Bergsma A. Capone W. Flegel L. Lanceri C. Nieuwenhuis J. Panman C. Santoni K. Winter I. Abt J. Aspiazu F. W. Büsser H. Daumann P. D. Gall T. Hebbeker F. Niebergall P. Schütt P. Stähelin P. Gorbunov E. Grigoriev V. Khovansky S. Krutchinin A. Maslennikov A. Rosanov L. Barone B. Borgia M. Diemoz U. Dore F. Ferroni E. Longo L. Luminari P. Monacelli F. de Notaristefani R. Santacesaria V. Valente The CHARM Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(4):497-522
A new beam-dump experiment has been performed at the CERN Super Proton Synchrotron using the CHARM neutrino detector. The instrumentation and the statistics have been significantly improved with respect to earlier experiments. For a neutrino energy above 20 GeV the asymmetry of the prompt muon-neutrino and electron-neutrino fluxes \([(v_\mu + \bar v_\mu ) - (v_e + \bar v_e )]/[(v_\mu + \bar v_\mu ) + (v_e + \bar v_e )]\) is found to be 0.20±0.10 (stat.)±0.05 (syst.), and the asymmetry of prompt antineutrino and neutrino fluxes for muonneutrinos \((v_\mu - \bar v_\mu )/(v_\mu + \bar v_\mu )\) is 0.02±0.16 (stat.)±0.02 (syst.) in agreement with our previous results. For the cross-section times branching ratio for charm production and semileptonic decay we obtain a value of \(\sigma \times BR\left[ {D(\bar D) \to v_e (\bar v_e ) X} \right] = 1.9 \pm 0.2 \pm 0.2\mu b\) per nucleon. We find no evidence forv τ orv x interactions. The \((v_\tau + \bar v_\tau )\) flux is less than 21% of the total prompt neutrino flux. We derive an improved limit on the branching ratio \(\pi ^0 \to v\bar v\) of 6.5×10?6, and as a verification of the universality of the neutral weak coupling we find \(g_{v_e \bar v_e } /g_{v_\mu \bar v_\mu } = 1.05_{ - 0.18}^{ + 0.15} \) . 相似文献
687.
R. Albrecht T. C. Awes C. Baktash P. Beckmann F. Berger R. Bock G. Classon L. Dragon R. L. Ferguson A. Franz S. Garpman R. Glasow H. A. Gustafsson H. H. Gutbrod K. H. Kampert B. W. Kolb P. Pristiansson I. Y. Lee H. L?hner I. Lund F. E. Obenshain A. Oskarsson I. Ottrlund T. Peitzmann S. Persson F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo H. R. Schmidt T. Siemiarczuk S. P. Sorensen E. Stenlung G. R. Young WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(1):97-103
Transverse momentum (p T) distributions fo inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and are measured with a lead glass calorimeter in 60 and 200A·Gev16O+nucleus and and proton+nucleus reactions. Inclusive photon distributions are compared for central and peripheral reactions. The degree of centrality is determined either from the charged particle multiplicity or from the remaining projectile energy in the forward direction. Deviations from a nucleus+nucleus interaction model based upon linear extrapolation from p+p reactions are observed in central16O+Au data. The variation of theaverage transverse momentum is investigated as function of centrality. The target-mass and energy dependence of π0 p T distributions are presented. For16O+Au a change of slope in these distributions is observed atp t ≈0.8 GeV/c compatible with hydrodynamic expansion models. 相似文献
688.
The CHORUS experiment is designed to search for νμ → ντ oscillation with a hybrid detector system containing 800 kg nuclear emulsions as target and vertex detector. Run I (320 000 recorded νμCC in 1994/5) and more than half of the run II (460 000 νμCC in 1996/7) data taking have been successfully completed. Approximately 80 000 events have been analyzed so far, searching for
and τ− → h− (nπ0) ντ decays. No candidate has been found, leading to a limit sin2 2θμτ ≤ 4.5 10−3 for large Δm2. 相似文献
689.
We present the results of the search for supermassive magnetic monopoles with the MACRO experiment. Our detector is equipped with three independent subdetectors (liquid scintillation counters, limited streamer tubes and nuclear track detectors), operating in different ranges of monopole velocity. In several years of data taking no candidates were found; the present flux upper limits are the level of half the Parker Bound for β > 10−4; for 10−4 < β < 5 × 10−2 the limit is the best existing. 相似文献
690.
T. Aziz J. L. Bailly S. Banerjee W. Bartl F. Bruyant B. Buschbeck C. Caso H. Dibon F. J. Diez-Hedo B. Epp A. Ferrando F. Fontanelli S. N. Ganguli I. V. Gorelov A. Gurtu P. Herquet J. Hrubec V. Khalatyan E. Kistenev S. Kitamura J. M. Kohli D. Kuhn J. MacNaughton P. K. Malhotra J. C. Marin S. Matsumoto I. S. Mittra L. Montanet G. Neuhofer P. Porth T. Rodrigo J. M. Salicio J. B. Singh S. Squarcia V. Stopchenko K. Takahashi U. Trevisan T. Tsurugai T. Yamagata G. Zholobov S. A. Zotkin EHS-RCBC Collaboration 《Zeitschrift fur Physik C Particles and Fields》1986,30(3):381-389
We have studied the inclusive production of strange meson and baryon resonances in 360 GeV/cpp interactions. Cross sections forK *+(892) andK *?(892) are estimated to be 4.42±0.62 mb and 2.54±0.47 mb respectively and those for∑ +(1385) and∑ ?(1385) are 0.67±0.11 mb and 0.26±0.07 mb respectively. Longitudinal and transverse momentum distributions forK *(892) and Σ(1385) are presented, as well as for their decay productsK 0 and Λ. An estimation is given on theK *(1430) and∑ *(1915) productions. 相似文献