57 research outputs found

    Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA

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    An investigation of the hadronic final state in diffractive and non--diffractive deep--inelastic electron--proton scattering at HERA is presented, where diffractive data are selected experimentally by demanding a large gap in pseudo --rapidity around the proton remnant direction. The transverse energy flow in the hadronic final state is evaluated using a set of estimators which quantify topological properties. Using available Monte Carlo QCD calculations, it is demonstrated that the final state in diffractive DIS exhibits the features expected if the interaction is interpreted as the scattering of an electron off a current quark with associated effects of perturbative QCD. A model in which deep--inelastic diffraction is taken to be the exchange of a pomeron with partonic structure is found to reproduce the measurements well. Models for deep--inelastic epep scattering, in which a sizeable diffractive contribution is present because of non--perturbative effects in the production of the hadronic final state, reproduce the general tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil

    Đ Đ°Đ·Ń€Đ°Đ±ĐŸŃ‚ĐșĐ° ĐžĐœŃ‚Đ”Ń€Đ°ĐșтоĐČĐœĐŸĐč ĐŒĐŸĐŽĐ”Đ»ĐžŃ€ŃƒŃŽŃ‰Đ”Đč ŃĐžŃŃ‚Đ”ĐŒŃ‹ Ń‚Đ”Ń…ĐœĐŸĐ»ĐŸĐłĐžĐž ĐœĐžĐ·ĐșĐŸŃ‚Đ”ĐŒĐżĐ”Ń€Đ°Ń‚ŃƒŃ€ĐœĐŸĐč сДпарацОО газа

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    We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≀ W Îłp ≀ 180 GeV and Q 2 â‰Č 4 GeV 2 . Using the flux of quasi-real photons with Q 2 â‰Č 4 GeV 2 , a total production cross section of σ ( Îłp → J / ψX ) = (56±13±14) nb is derived at an average W Îłp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∄ t ∄) below a ∄ t ∄ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2

    Jets and energy flow in photon-proton collisions at HERA

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    Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to \overline{p}p data and QCD calculations. The comparisons show that the \gamma p events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections d\sigma/dE_T^{jet} and d\sigma/d\eta^{jet} are measured

    Electroweak parameters of the z0 resonance and the standard model

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    Contains fulltext : 124399.pdf (publisher's version ) (Open Access

    The Tracking, calorimeter and muon detectors of the H1 experiment at HERA

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    Technical aspects of the three major components of the H1 detector at the electron-proton storage ring HERA are described. This paper covers the detector status up to the end of 1994 when a major upgrading of some of its elements was undertaken. A description of the other elements of the detector and some performance figures from luminosity runs at HERA during 1993 and 1994 are given in a paper previously published in this journal.0400 auteursSCOPUS: ar.jinfo:eu-repo/semantics/publishe

    A measurement of the proton structure function F2(x, Q2)

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    Elastic photoproduction of ρ0\rho^{0} mesons at HERA

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    Observation of hard processes in rapidity gap events in Îł\gammap 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

    A Search for selectrons and squarks at HERA

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