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Exclusive processes at HERA  [PDF]
Robert Ciesielski,for the H1,ZEUS Collaborations
Physics , 2008,
Abstract: An increased precision of HERA data allows studies of exclusive processes in their transition from soft to hard interactions as well as in the pQCD domain. The recent measurements of vector meson production and Deeply Virtual Compton Scattering (DVCS) performed by the H1 and ZEUS experiments are reported and compared to pQCD expectations.
Exclusive processes in diffraction at HERA
Polini, A.;,;,;
Brazilian Journal of Physics , 2007, DOI: 10.1590/S0103-97332007000500036
Abstract: recent results from the h1 and zeus experiments on exclusive processes in diffractive ep collisions at hera are reviewed. the measurements discussed here include dijets and charm in photoproduction as well as in deep inelastic scattering. such processes are sensitive to the partonic structure of the diffractive exchange, particularly to the gluon content, and represent complementary tests for the validity of qcd factorization in diffraction. the measurements are compared to theoretical models, including nlo predictions, using the most recent diffractive parton densities as extracted from inclusive measurements. recent results on exclusive vector meson production and deeply virtual compton scattering are also presented.
Reggeon and pion contributions in semi-exclusive diffractive processes at HERA  [PDF]
K. Golec-Biernat,J. Kwieciński,A. Szczurek
Physics , 1997, DOI: 10.1103/PhysRevD.56.3955
Abstract: A detailed analysis of semi-exclusive diffractive processes in e-p DIS at HERA, with the diffractive final states in the forward direction is presented. The contributions of the subleading f_2, \omega, a_2, \rho reggeons and the pion exchanges to the diffractive structure function with the forward proton or neutron are estimated. It is found that the (a_2,\rho) reggeons are entirely responsible for the forward neutron production at x_P < 10^{-3}. The \pi N production in the forward region is estimated using the Deck mechanism. The significance of this reaction for the processes measured at HERA, especially with the leading neutron, is discussed.
Electroweak Measurements  [PDF]
Cristinel Diaconu
Physics , 2005, DOI: 10.1142/S0217751X06032617
Abstract: The measurements of electroweak sector of the Standard Model are presented, including most recent results from LEP, Tevatron and HERA colliders. The robustness of the Standard Model is illustrated with the precision measurements, the electroweak fits and the comparisons to the results obtained from low energy experiments. The status of the measurements of the $W$ boson properties and rare production processes involving weak bosons at colliders is examined, together with the measurements of the electroweak parameters in $ep$ collisions.
Electroweak constraints from HERA  [PDF]
Elisabetta Gallo,for the ZEUS Collaboration,H1 Collaboration
Physics , 2008,
Abstract: A summary of the electroweak results at HERA is presented.
Exclusive Diffraction at HERA and Beyond  [PDF]
S. Fazio
Physics , 2010,
Abstract: The exclusive diffractive production of vector mesons and real photons in ep collisions has been studied at HERA in a wide kinematic range. Here the most recent experimental results are presented together with a Regge-type model and projects for new diffractive studies at LHC.
Electroweak Results from HERA  [PDF]
Aleksander Filip Zarnecki
Physics , 2013,
Abstract: Neutral and charged current deep inelastic ep scattering with longitudinally polarised lepton beams has been studied with the H1 and ZEUS detectors at HERA. The differential cross sections were measured in the range of four-momentum transfer squared, Q^2, up to 50'000 GeV^2, where electroweak effects become clearly visible. The measurements were used to determine the structure function xF_3 and to constrain vector and the axial-vector couplings of the light quarks to the Z^0 boson. The polarisation dependence of the charged current total cross section was also measured. Limits on flavour changing neutral current processes were computed from the search for single-top production. The elastic Z^0 production cross section was measured to be in agreement with the SM prediction. Limits on new physics phenomena at high Q^2 were also derived within the general framework of four-fermion eeqq contact interactions.
Semi-Exclusive Production of Photons at HERA  [PDF]
Paul Hoyer,Martin Maul,Andreas Metz
Physics , 2000, DOI: 10.1007/s100520000467
Abstract: We study the feasibility of measuring semi-exclusive photon production \gamma + p \to \gamma + Y at HERA. The cross section of photons produced at large transverse momenta, recoiling off an inclusive system Y of limited mass, can without photon isolation cuts be simply expressed in terms of hard pQCD subprocesses and standard target parton distributions. With the help of event generators we identify the kinematic region where quark and gluon fragmentation processes can be neglected. The cross section in this semi-exclusive region is large enough to be measured with an upgraded HERA luminosity of L = 100/pb. The subprocesses of lowest order in \alpha_s are suppressed at low recoil masses M_Y, compared to higher order gluon exchange, i.e. BFKL contributions. The distinct M_Y-dependence makes it possible to determine experimentally the kinematic range where the higher order processes dominate.
Searches and electroweak measurements at HERA  [PDF]
Sascha Caron
Physics , 2004,
Abstract: The H1 and ZEUS collaborations have used the HERA I data to search for physics beyond the SM and to test electroweak physics in electron-proton collisions. The new period of data taking (HERA II) has started and first HERA II analyses become available. An overview is given of recent highlights, including isolated lepton and multi-lepton events, tests of models of new physics and the first systematic search for deviations in all final states with high transverse momentum.
Experimental Studies of Diffractive Processes at HERA  [PDF]
A. A. Savin,on behalf of the H1,ZEUS collaborations
Physics , 2001,
Abstract: Diffractive processes in photon-proton interactions at HERA offer the opportunity to improve the understanding of the transition between the soft, non-perturbative regime in hadronic interactions at $Q^2 = 0$ and the perturbative region at high $Q^2$. Recent experimental results from HERA on inclusive diffractive scattering, exclusive vector meson production and the properties of the hadronic final state in diffraction are reviewed. The results are discussed in the context of current theoretical models.
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