2,713 research outputs found

    (Some of) recent γγ\gamma\gamma measurements from LEP

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    Inclusive measurement of J/ΨJ/\Psi (DELPHI), search for ηb\eta_b (ALEPH) and measurement of the cross-section of the double-tagged γγ\gamma\gamma events (ALEPH) are briefly overviewed.Comment: 6 pages, 2 figures in ps and 5 in eps, talk given at XXXI International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong China. see http://ismd31.ccnu.edu.cn

    Helix string fragmentation and charged particle correlations with ATLAS

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    Correlations between charged particles provide important insight about the hadronization process. The analysis of the momentum difference between charged hadrons in pppp, pp-lead, and lead-lead collisions at LHC is performed by the ATLAS Collaboration in order to study the dynamics of hadron formation. The spectra of correlated hadron chains are explored and compared to the predictions based on the quantized fragmentation of a three dimensional QCD helix string. This provides an alternative view of the two-particle correlation phenomenon typically attributed to the Bose-Einstein interference.Comment: 5 pages, 3 figures. Proceedings ISMD202

    Photoproduction of J/ψJ/\psi in association with a ccˉc\bar{c} pair

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    Based on the color-singlet model, we investigate the photoproduction of J/ψJ/\psi associated with a ccˉc \bar{c} pair with all subprocesses including the direct, single-resolved, and double-resolved channels. The amplitude squared of these subprocesses are obtained analytically. By choosing corresponding parameters, we give theoretical predictions for the J/ψJ/\psi transverse momentum distributions both at the LEPII and at the future photon colliders for these subprocesses. The numerical results show that at the LEPII these processes can not give enough contributions to account for the experimental data, and it indicates that the color-octet mechanism may still be needed. At the photon collider with the laser back scattering photons, the resolved photon channe will dominate over the direct one in small and moderate ptp_t regions with large s\sqrt{s}. By measuring the J/ψJ/\psi production associated with a ccˉc\bar{c} pair, this process can be separated from the inclusive J/ψJ/\psi production and may provide a new chance to test the color-singlet contributions.Comment: 16 pages, 7 figure

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS