Related papers: Direct vs. resolved photon: an exercise in factori…
The interaction of electrons with strong laser fields is usually treated with semiclassical theory, where the laser is represented by an external field. There are analytic solutions for the free electron wave functions, which incorporate…
A new next-to-leading order Monte Carlo program for the calculation of jet cross sections in photoproduction is described. The contributions from both resolved and direct components are included to O(\alpha \alpha_s^2). Properties of the…
Using an eikonal analysis, we examine the validity of the factorization theorem for nucleon-nucleon, gamma p and gamma gamma collisions. As an example, using the additive quark model and meson vector dominance, we directly show that for all…
We study jet production in photon-photon reactions at the next-to-leading logarithm accuracy. The discussion of the theoretical uncertainties and the role of the quark and gluon distributions in the photon is emphasized. The phenomenology…
In the literature, one often finds calculations of (e,e'p) reactions at GeV energies using the factorization approach. Factorization implies that the differential cross section can be written as the product of an off-shell electron-proton…
We investigate the polarized photon structure functions $g_1^\gamma$ and $g_2^\gamma$ which can be studied in the future polarized version of ep or e$^+$e$^-$ colliders. The NLO QCD calculations of $g_1^\gamma$ and the possible twist-3…
It is shown that direct photons provide a leading twist mechanism for diffractive jet production in which the jets carry away all of the momentum lost by the proton. Two-photon processes are thus expected to asymptotically dominate…
After giving a very brief introduction to the resolved photon processes, I will summarise the latest experimental information from HERA, on resolved photon contribution to large pt jet production as well as to direct photon production. I…
We calculate diffractive dijet production in deep-inelastic scattering at next-to-leading order of perturbative QCD, including contributions from direct and resolved photons, and compare our predictions to preliminary data from the H1…
It has been found that recent results on forward jet production from deep inelastic scattering can neither be reproduced by models which are based on leading order alpha_s QCD matrix elements and parton showers nor by next-to-leading order…
It is shown that by assuming Gribov factorization to hold at low $x$ one obtains a simple relation between the structure function of the proton and that of the photon. By interpreting an observed structure in deep inelastic scattering (DIS)…
Direct photon production is an important observable in heavy ion collisions as photons are penetrating and therefore largely insensetive to final state effects that lead to jet quenching. Measurements of the fragmentation component to…
We show that the data on $\gamma p$ and $\gamma\gamma$ interactions can be derived from the $pp$ and $\bar p p$ forward scattering amplitudes using vector meson dominance and the additive quark model. The nucleon-nucleon data are…
We derive expressions for the differential distributions and the total cross section of double- parton interaction in direct photon interaction with proton and nuclei. We demonstrate that in this case the cross section is more directly…
A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. Based on this picture, we previously presented a model for gamma-p events that is based on the presence…
We investigate the effects of photon radiation on deep-inelastic $\re\gamma$ scattering. Depending on the set of variables chosen, we find appreciable effects in the kinematic region accessible at LEP2. Convenient analytic results for…
In this paper, we report on the calculation of the cross section of J/\Psi plus jet inclusive production in direct two-photon collisions at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics…
Recent results of open charm and beauty production in electron proton scattering at HERA are presented. In photoproduction, the measured cross sections for charm exceed fixed order NLO QCD calculations. Experimental evidence supports the…
The problem of dealing with the resolved photon contribution to $P^2$-integrated $ep$ cross sections is discussed. Suitable approximations have to be found, since no parametrization of the photon structure function in the full range of…
Direct photon production in association with a heavy quark can serve as an excellent tool for the study of the heavy quark distributions. Currently it is believed that heavy quarks are produced radiatively inside the nucleon, and so there…