102 research outputs found

    High-Energy Forward Scattering and the Pomeron: Simple Pole versus Unitarized Models

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    Using the largest data set available, we determine the best values that the data at t=0 (total cross sections and real parts of the hadronic amplitudes) give for the intercepts and couplings of the soft pomeron and of the rho/omega and a/f trajectories. We show that these data cannot discriminate between a simple-pole fit and asymptotic log square s and log s fits, and hence are not sufficient to reveal the ultimate nature of the pomeron. However, we evaluate the existing evidence (factorization, universality, quark counting) favouring the simple-pole hypothesis. We also examine the range of validity in energy of the fits, and show that one cannot rely on such fits in the region sqrt(s)<9 GeV. We also establish bounds on the odderon and the hard pomeron.Comment: 20 pages, 10 figures. Predictions of Table 4 corrected and acknowledgements adde

    Soft Pomeron and Lower-Trajectory Intercepts

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    We present a preliminary report on the determination of the intercepts and couplings of the soft pomeron and of the rho/omega and f/a trajectories from the largest data set available for all total cross sections and real parts of the hadronic amplitudes. Factorization is reasonably satisfied by the pomeron couplings, which allows us to make predictions on gamma gamma and gamma p total cross sections. In addition we show that these data cannot discriminate between fits based on a simple Regge pomeron-pole and on an asymptotic log^2s-type behaviour, implying that the effect of unitarisation is negligible. Also we examine the range of validity in energy of the fit, and the bounds that these data place on the odderon and on the hard pomeron.Comment: 13 pages, LaTeX, 14 figures. Presented by K. Kang at a 4th Workshop on Quantum Chromodynamics, June 1 - 6, 1998, The American University of Paris, Paris, France, and at the 4th Workshop on Small-x and Diffractive Physics, September 17 - 20, 1998, Fermi National Accelerator Laboratory, Batavia, I

    Analytic Amplitude Models for Forward Scattering

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    We report on fits of a large class of analytic amplitude models for forward scattering against the comprehensive data for all available reactions. To differentiate the goodness of the fits of many possible parametrizations to a large sample of data, we developed and used a set of quantitative indicators measuring statistical quality of the fits over and beyond the typical criterion of the X2/dof\Chi^2 /dof. These indicators favor models with a universal log2s log^2 s Pomeron term, which enables one to extend the fit down to s=4\sqrt s = 4 GeV.Comment: 13 pages, COMPETE Collaboration, talk presented at the 9th International Conference (Blois Workshop) on Elastic and Diffractive Scatterin

    Analytic parametrizations of the non-perturbative Pomeron and QCD-inspired models

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    We consider several classes of analytic parametrizations of hadronic scattering amplitudes, and compare their predictions to all available forward data (proton- proton, antiproton-proton, pion-proton, kaon-proton, photon-proton, photon- photon, sigma-proton). Although these parametrizations are very close for energy larger than 9 GeV, it turns out that they differ markedly at low energy, where a universal Pomeron term ~(ln s)**2 enables one to extend the fit down to 4 GeV.Comment: 11 pages, 2 tables, Presented at the 9th Blois Workshop on Elastic and Diffractive Scattering, Pruhonice, Czech Republic, 9-15 June 200

    New measures of the quality and of the reliability of fits applied to forward hadronic data at t=0

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    We develop five new statistical measures of the quality of fits, which we combine with the usual confidence level to determine the models which fit best all available data for total cross sections and for the real part of the forward hadronic amplitude.Comment: 7 pages, presented by J.R. Cudell on behalf of the COMPETE collaboration at the 6th workshop on non-perturbative QCD, American University of Paris, 5-9 June 200

    Forward observables at RHIC, the Tevatron run II and the LHC

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    We present predictions on the total cross sections and on the ratio of the real part to the imaginary part of the elastic amplitude (rho parameter) for present and future pp and pbar p colliders, and on total cross sections for gamma p -> hadrons at cosmic-ray energies and for gamma gamma -> hadrons up to sqrt(s)=1 TeV. These predictions are based on a study of many possible analytic parametrisations and invoke the current hadronic dataset at t=0. The uncertainties on total cross sections, including the systematic theoretical errors, reach 1% at RHIC, 3% at the Tevatron, and 10% at the LHC, whereas those on the rho parameter are respectively 10%, 17%, and 26%.Comment: 11 pages, 2 figures, LaTeX, presented at the Second International "Cetraro" Workshop & NATO Advanced Research Workshop "Diffraction 2002", Alushta, Crimea, Ukraine, August 31 - September 6, 200
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