3,073 research outputs found

    Can the "standard" unitarized Regge models describe the TOTEM data?

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    The standard Regge poles are considered as inputs for two unitarization methods: eikonal and U-matrix. It is shown that only models with three input pomerons and two input odderons can describe the high energy data on pppp and pˉp\bar pp elastic scattering including the new data from Tevatron and LHC. However, it seems that the both considered models (eikonal and U-matrix) require a further modification (e.g., to explore nonlinear reggeon trajectories and/or nonexponential vertex functions) for a more satisfactory description of the data at 19.0 GeV≤s≤\leq \sqrt{s}\leq 7 TeV and 0.01 ≤∣t∣≤\leq |t|\leq 14.2 GeV2^{2}.Comment: 11 pages, 7 figures, typos are corrected, minor corrections in the text, No changes in results and conclusion. To appear in EP

    Impact analysis of TOTEM data at the LHC: black disk limit exceeded

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    We discuss the profile of the impact--parameter dependent elastic scattering amplitude. Extraction of impact-parameter dependence from the dataset with inclusion of the experimental data on elastic scattering at the LHC energies helps to reveal the asymptotics of hadron interactions. Analysis of the data clearly indicates that the impact-parameter elastic scattering amplitude exceed the black disk limit at the LHC energy 7TeV and the inelastic overlap function reaches its maximum value at b>0b>0Comment: 5 pages, 5 figure

    On jet structure in heavy ion collisions

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    The LHC data on jet fragmentation function and jet shapes in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in the frameworks of PYQUEN jet quenching model. A specific modification of longitudinal and radial jet profiles in most central PbPb collisions as compared with pp data is close to that obtained with PYQUEN simulations taking into account wide-angle radiative and collisional partonic energy loss. The contribution of radiative and collisional loss to the medium-modified intra-jet structure is estimated.Comment: 9 pages including 3 figures as EPS-files; prepared using LaTeX package for publication in the European Physical Journal

    Choosing an Evaluation Theory: A Supplement to Evaluation Roots (3rd Edition)

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    Background: Unlike scientific theories, evaluation theories are prescriptive: a set of actions and approaches that should be followed when conducting an evaluation. While evaluation theorists have offered a variety of writings describing their theories and approaches, few have offered a specific outline of what the theory looks like in practice. Thus, Alkin and Christie formulated a book to aid evaluators in how to apply theories in evaluations (Alkin & Christie, forthcoming). This book culminates in a series of prototypes that outline each theory’s goals, appropriate contexts, prescriptions, and observable actions in application. Purpose: In order to aid evaluators in applying theories, this article seeks to provide a basis for comparison that can be used to help evaluators select which theory would be most appropriate in their practice. Setting: This comparison can be applied in any setting where evaluations fit the context prescribed by each of the theories. Intervention: Not applicable. Research Design: Not applicablre. Data Collection and Analysis: Not applicable. Findings: In order for theories to influence practice effectively, theories must be displayed in a way that allows for easy comparison. This comparison of three theory prototypes demonstrates that prototypes can be an effective way for selecting a prescriptive theory when conducting an evaluation. Keywords: prescriptive theories; practice; empowerment evaluation; learning centered model; developmental evaluatio

    Dispersion relations for meson-proton and proton-proton forward elastic scattering

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    An analysis of the data on forward pp,pˉp,π±ppp, \bar pp, \pi^{\pm}p and K±pK^{\pm}p scattering is performed making use of the single- and double-subtraction integral and comparing with derivative dispersion relations for amplitudes. Various pomeron and odderon models for the total cross sections are considered and compared. The real part of the amplitude is calculated via dispersion relations. It is shown that the integral dispersion relations lead to a better description of the data for s>\sqrt{s}>5 GeV. Predictions of the considered models for the TOTEM experiment at LHC energies are givenComment: 15 pages, 12 figures. Presented at the workshop "30 years of strong interactions", Spa, Belgium, 6-8 April 2011. Version published in Few Body Systems: typos correcte

    Forward physics at the LHC (Elba 2010)

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    First measurement of Ξc0\Xi_{\rm c}^0 production in pp collisions at s\mathbf{\sqrt{s}} = 7 TeV

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    The production of the charm-strange baryon Ξc0\Xi_{\rm c}^0 is measured for the first time at the LHC via its semileptonic decay into e+Ξ−νe^+\Xi^-\nu_{\rm e} in pp collisions at s=7\sqrt{s}=7 TeV with the ALICE detector. The transverse momentum (pTp_{\rm T}) differential cross section multiplied by the branching ratio is presented in the interval 1 << pTp_{\rm T} << 8 GeV/cc at mid-rapidity, ∣y∣|y| << 0.5. The transverse momentum dependence of the Ξc0\Xi_{\rm c}^0 baryon production relative to the D0^0 meson production is compared to predictions of event generators with various tunes of the hadronisation mechanism, which are found to underestimate the measured cross-section ratio.Comment: 22 pages, 6 captioned figures, 1 table, authors from page 17, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/412
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