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Abstract:

Deeply virtual Compton scattering, γ*p→γp has been measured in e⁺p collisions at HERA with the ZEUS detector using an integrated luminosity of 61.1 pb^-1. Cross sections are presented as a function of the photon virtuality, Q², and photon-proton centre-of-mass energy, W, for a wide region of the phase space, Q² > 1.5GeV² and 40 < W < 170GeV. A subsample of events in which the scattered proton is measured in the leading proton spectrometer, corresponding to an integrated luminosity of 31.3 pb^-1, is used for the first direct measurement of the differential cross section as a function of t, where t is the square of the four-momentum transfer at the proton vertex. © SISSA 2009.

Abstract:

Direct measurements of the proton structure function FL have been performed in deep inelastic ep scattering at low x at HERA. The FL values are extracted by the H1 and ZEUS collaborations from the cross sections measured at fixed x and Q2 but different y values. This is achieved by using data sets collected with three different proton beam energies. The H1 and ZEUS results are consistent with each other and exhibit a non-zero FL. The measurements are also consistent with the previous indirect determinations of FL by H1. The results confirm DGLAP NLO and NNLO QCD predictions for FL(x,Q2), derived from previous HERA data, which are dominated by a large gluon density at low x.

Abstract:

When particle physic started, cosmic ray were used as source of new particles. Nowadays particle physic is a fundamental key to understand the nature of the very high energy cosmic rays. Above 1014 eV, primary cosmic rays are detected via air showers whose development strongly rely on the physic of the forward region of hadronic interactions as tested in the HERA and LHC experiments. After an introduction on air shower phenomenology, we will review how HERA and LHC can constrain the physic used both in hadronic interaction model, or for photon or neutrino primaries.

Abstract:

The semi-inclusive reaction e+p→e+Xp was studied with the ZEUS detector at HERA with an integrated luminosity of 12.8 pb -1. The final-state proton, which was detected with the ZEUS leading proton spectrometer, carried a large fraction of the incoming proton energy, xL > 0.32, and its transverse momentum squared satisfied p 2T < 0.5GeV2; the exchanged photon virtuality, Q2, was greater than 3GeV2 and the range of the masses of the photon-proton system was 45 < W < 225GeV. The leading proton production cross section and rates are presented as a function of xL, p2 T , Q2 and the Bjorken scaling variable, x. © SISSA 2009.