9 research outputs found

    Observation of hard processes in rapidity gap events in gamma-p interactions at Hera

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    Observation of hard processes in rapidity gap events in gamma p interactions at HERA

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    Events with no hadronic energy flow in a large interval of pseudo-rapidity in the proton direction are observed in photon-proton interactions at an average centre of mass energy 〈sγp\sqrt {s_{ \gamma p}} 〉 of 200 GeV These events are interpreted as photon diffractive dissociation. Evidence for hard scattering in photon diffractive dissociation is demonstrated using inclusive single particle spectra, thrust as a function of transverse energy, and the observation of jet production. The data can be described by a Monte Carlo calculation including hard photon-pomeron scattering

    Determination of the strong coupling constant from jet rates in deep inelastic scattering

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    Jet rates in deep inelastic electron proton scattering are studied with the H1 detector at HERA for momentum transfers squared between 10 and 4000 GeV2^2 . It is shown that they can be quantitatively described by perturbative QCD in next to leading order making use of the parton densities of the proton and with the strong coupling constant αs\alpha_s as a free parameter. The measured value, αs(MZ2)=0.123±0.018\alpha_s ( M_Z^2 ) = 0.123 ± 0.018, is in agreement both with determinations from e+ee^+ e^− annihilation at LEP using the same observable and with the world average

    A measurement of the proton structure function f2(x.q2)f_2(x. q^2)

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    A measurement of the proton structure function F_{\!2}(x,Q^2) is reported for momentum transfer squared Q^2 between 4.5 GeV^2 and 1600 GeV^2 and for Bjorken x between 1.8\cdot10^{-4} and 0.13 using data collected by the HERA experiment H1 in 1993. It is observed that F_{\!2} increases significantly with decreasing x, confirming our previous measurement made with one tenth of the data available in this analysis. The Q^2 dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the "diffractive" contribution to F_{\!2}

    A measurement of the proton structure function f2(x.q2)f_2(x. q^2)

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    A measurement of the proton structure function F_{\!2}(x,Q^2) is reported for momentum transfer squared Q^2 between 4.5 GeV^2 and 1600 GeV^2 and for Bjorken x between 1.8\cdot10^{-4} and 0.13 using data collected by the HERA experiment H1 in 1993. It is observed that F_{\!2} increases significantly with decreasing x, confirming our previous measurement made with one tenth of the data available in this analysis. The Q^2 dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the "diffractive" contribution to F_{\!2}

    Photoproduction of K"0 and #LAMBDA# at HERA and a comparison with deep inelastic scattering

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    Inclusive K"0 and #LAMBDA# photoproduction has been investigated at HERA with the H1 detector at an average photon-proton center of mass energy of 200 GeV in the transverse momentum range 0.5 < p_t < 5 GeV. The production rates as a function of p_t and center of mass rapidity are compared to those obtained in deep inelastic scattering at left angle Q"2 right angle = 23 GeV"2. A similar comparison is made of the rapidity spectra of charged particles. The rate of strangeness photoproduction is compared with pp measurements. The observations are also compared with next-to-leading order QCD calculations and the predictions of a Monte Carlo model. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

    Bose-Einstein correlations in deep inelastic e p scattering at HERA

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    Two-particle correlations in invariant mass are studied separately for like-sign and unlike-sign charged particles produced in deep inelastic positron-proton scattering in a new kinematical domain. The data were taken with the H1 detector at the HERA storage ring in 1994, in which 27.5 GeV positrons collided with 820 GeV protons at a centre of mass energy sqrt{s}=300 GeV. The observed enhancement of the like-sign correlations at low invariant masses is related to the dimensions of the hadronic source. The data are compared to different QCD models where the hadronization is performed with the string-fragmentation model. Results are presented for the first time separately for diffractive and non-diffractive scattering, in domains of four-momentum transfer, Bjorken-x, and hadronic center of mass energy, and in intervals of charged particle multiplicity. The observed source radii do not differ strongly from those measured in lower energy lepton-nucleon inelastic scattering, and e^+e^- annihilation.Comment: 36 pages, 10 Figure

    Bacteraemia in man and animals: An overview

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