The electroproduction of rho mesons with proton diffractive dissociation for Q^2 > 7 GeV^2 and the elastic electroproduction of Phi mesons for Q^2 > 6 Gev^2 are studied in e^+ p collisions at HERA with the H1 detector, for an integrated luminosity of 2.8 pb-1. The dependence of the cross sections on P_t^2 and Q^2 is measured, and the vector meson polarisation obtained. The cross section ratio between proton dissociative and elastic production of rho mesons is measured and discussed in the framework of the factorisation hypothesis of diffractive vertices. The ratio of the elastic cross section for Phi and rho meson production is investigated as a function of Q^2.
Corrected PT**2 distribution for RHO production from the proton dissociative sample. Statistical errors only.
Cross sections and ratio of proton dissociative to elastic cross sections.
Cross sections and ratio of proton dissociative to elastic cross sections.
This paper presents results on charm photoproduction in the energy interval 40 to 160 GeV, obtained from the high-statistics charm samples of the NA 14/2 experiment at CERN. We measure the charm cross-section, the distributions inxF andp2T and various production ratios and charge asymmetries. The total non-diffractive open-charm cross-section per nucleon is measured to be\(\sigma _{(\gamma N \to c\bar cX)} \) at 〈Eγ〉 =100 GeV. We discuss the photoproduction of charm in terms of theoretical and phenomenological models. We compare the measuredp2T andxF distributions with first-order QCD calculations of photon-gluon fusion and obtain a value for the charm-quark mass ofmc=1.5+0.2−0.1GeV/c2.
D0 cross section assuming branching ratio of D0 --> K- PI+ of 3.65 +- 0.21 PCT.
D+(-) cross section assuming branching ratio of D+ --> K- PI+ PI+ of 8.0 +0.8,-0.7 PCT.
Total non diffractive open charm production cross section allowing for contributions for other charmed particles (D/S and LAMBDA/C). Comparison of data with first order QCD leads to a predicted charm quark mass of 1.5 +0.2,-0.1 GeV.
We present an experimental study of jetproduction in photon-photon interactions for 0.1≲Q2≲120 GeV2 and jet transverse momentum,pT, up to 5 GeV/c. At alQ2, the data show a highpT, tail, characteristic of a point-like interaction. The jet production cross-section approaches the quarkparton model (QPM) expectation as either jetpT orQ2 increases. Overall, the data are well described in both total cross-section and event topology by the sum of a vector-dominance model and a point-like interaction, represented by the QPM.
No description provided.
We present new high statistics data on hadron production in photon-photon reactions. The data are analyzed in terms of an electron-photon scattering formalism. The dependence of the total cross section of Q 2 , the four-momentum transfer squared of the scattered electron, and on the mass W of the hadronic system is investigated. The data are compared to predictions from Vector-Meson Dominance and the quark model.
No description provided.
DEPENDENCE ON VISIBLE HADRONIC INVARIANT MASS.
Data read from graph.
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