Related papers: Two-photon cross-sections from the saturation mode…
The shapes of invariant differential cross section for charged hadron production as function of hadron's transverse momentum and rapidity in ep collisions at HERA machine are considered. The particle spectra shapes observed in pp and…
We employ values of the colour dipole cross section extracted from electroproduction and photoproduction data to show that gluon saturation effects are not required by the current HERA data but will become important in the THERA energy…
Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in…
The hadronic structure function of the photon F_2^gamma is measured as a function of Bjorken x and of the factorisation scale Q^2 using data taken by the OPAL detector at LEP. Previous OPAL measurements of the x dependence of F_2^gamma are…
Using a momentum space model for the dipole scattering amplitude we present an analysis of the saturation effects at LHC energies, describing the data on proton-proton and proton-lead collisions. The model is based on the asymptotic…
In the effective field theory framework the interaction between two heavy hadrons can be decomposed into a long- and a short-range piece. The long-range piece corresponds to the one-pion-exchange potential and is relatively well-known. The…
We perform joint fits using measurements of the proton structure functions $F_2(x,Q^2)$ and $F_L(x,Q^2)$, of the photon structure function $F_2^\gamma(x,Q^2)$ and of the total cross-sections $\sigma\left( \gamma p \rightarrow X\right)$ and…
The structure of both quasi-real and highly virtual photons is investigated using the reaction e+e- -> e+e-mu+mu-, proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at e+e- centre-of-mass…
Through a determination of the $S$-matrix element for the scattering of a localized colour dipole on a proton, we show that saturation effects can already be sizable at HERA. The saturation scale is found to be around 1-1.5 $GeV^2$ for the…
We analyse the dissociation of a photon in diffractive deep inelastic scattering in the kinematic regime where the diffractive mass is much bigger than the photon virtuality. We consider the dominant q\bar{q}g component keeping track of the…
The results of measurements of gamma-N total cross section, obtained by the method of photoproduction processes registration at the Baksan Underground Scintillation Telescope, are presented. These data at energies sqrt(s)=40-130 GeV confirm…
We investigate the role of unitarization effects in virtual photon-proton (\gamma^*p) interactions at small x. The q\bar{q}-fluctuation of the initial photon is separated into a small distance and a large distance component and a model for…
We discuss the role of fully heavy tetraquarks in ultraperipheral collisions $AA\to AA\, J/\psi J/\psi$ and $AA \to AA\, \gamma \gamma$. Two-photon couplings to scalar and tensor tetraquarks are considered. We use relatively recent results…
A model for both proton and photon total cross-sections is presented and compared with data. The model is based on the eikonal representation, with QCD mini-jets to drive the rise and soft gluon kt-resummation into the Infrared region to…
We study in the BFKL approach the total hadronic cross section for the collision of two virtual photons for energies in the range of LEP2 and of future linear colliders. The BFKL resummation is done at the next-to-leading order in the BFKL…
The cross-section for the process $\gamma + A \to \mu^+ + \mu^- + X$ is studied where the photon energy is of the order of several hundreds of GeV and where one of the leptons is scattered to large angles. This is of practical importance…
We study multi-photon effects in quantum electrodynamics in lepton photo-production on heavy nuclei and nuclear medium at high energies. We are interested in energy, charge density and nuclear geometry dependence of the cross sections. We…
This analysis provides new fits of the GBW model and the impact parameter-dependent saturation model (bSat or IP-Sat) to the leading neutron structure function HERA data in one pion exchange approximation. Both parametrizations of the…
The process e^+e^- -> gamma gamma (gamma) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 25.38 pb^{-1} taken at centre-of-mass energies of 130-172 GeV. The…
We consider the exclusive photoproduction of a $\pi^0 \gamma$ pair with large invariant mass, as a promising channel to study the effects of gluon saturation. It has recently been demonstrated that this process is incompatible with a…