Related papers: Twist-three effects in two-photon processes
The handbag mechanism for wide-angle exlusive scattering reactions is discussed and compared with other theoretical approaches. Its application to Compton scattering, meson photoproduction and two-photon annihilations into pairs of hadrons…
We review recent theoretical and experimental progress on the role of two-photon exchange (TPE) in electron-proton scattering at low to moderate momentum transfers. We make a detailed comparison and analysis of the results of competing…
The nucleon mass corrections are calculated to all polarized structure functions for neutral and charged current deep inelastic scattering in lowest order in the coupling constant. The impact of the target mass corrections on the general…
We study twist expansions for parton fragmentation functions based on the definition of the twist as an invariant matrix element of a light-cone, bilocal operator. The results are then applied to a method which might be used to extract…
The probabilistic model of parton distributions, previously developed by one of the authors, is generalized to include the transversity distribution. When interference effects are attributed to quark level only, the intrinsic quark motion…
The process in which a photon splits into three after the collision with a free electron (triple Compton effect) is the most basic process for the generation of a high-energy multi-particle entangled state composed out of elementary quanta.…
Interactions of virtual photons are analyzed in terms of photon structure. It is argued that the concept of parton distribution functions is phenomenologically very useful even for highly virtual photons involved in hard collisions. This…
The observation of the quark transversity distribution requires another soft object sensitive to the quark's transverse spin. Dihadron fragmentation functions represent a convenient tool to analyze partonic spin, which can influence the…
Transverse-momentum spectra in hard processes are typically described either in terms of intrinsic transverse momentum of partons, or in terms of perturbative radiation. The relation between these descriptions is discussed for the example…
We analyze in detail the problem of gauge invariance of the deeply vitual Compton scattering (DVCS) amplitude. Using twist 3 one-gluon exchange diagram contributions and the QCD equations of motion, we derive the general gauge invariant…
The single spin asymmetries for a longitudinally polarized lepton beam or a longitudinally polarized nucleon target in semi-inclusive deep-inelastic scattering are twist-3 observables. We study these asymmetries in a simple diquark…
We present a quark-parton model to describe polarized and unpolarized nucleon structure functions. The twist-two matrix elements for the QCD evolution analysis of lepton-hadron scattering are calculated within a light-front covariant quark…
The presence of two photon exchange in $ep$ elastic scattering and in the crossed processes ($\bar p +p\leftrightarrow \ell^+ +\ell^-$, $\ell=e$ or $\mu$) is discussed in terms of three complex amplitudes which are functions of two…
We study the polarized Drell-Yan processes from the collision of two spin-1/2 hadrons at order 1/Q based on the framework of transverse momentum dependent factorization.We give the complete twist-three results of total sixteen independent…
We discuss the elastic ed scattering beyond Born approximation. It is shown that the reaction amplitude contains six generalized form factors, but only three linearly independent combinations of them (we call them generalized charge,…
Quarks and gluon, as quantum particles, are subjects to various effects that go beyond the naive parton picture and are not captured by ordinary parton densities. In this work, we investigate the twist-three parton distribution functions,…
In order to study twist-3 and transverse momentum dependent parton distributions, we use light-front time-ordered pQCD at order $\alpha_s$ to calculate various distribution functions for a dressed quark target. This study enables us to…
The twist-2 contributions to the polarized structure functions in deep inelastic lepton--hadron scattering are calculated including the exchange of weak bosons and using both the operator product expansion and the covariant parton model. A…
The beam spin asymmetries of the reaction ep -> epg in the Bjorken regime were measured over a wide kinematical domain using the CLAS detector and a new lead-tungstate calorimeter. Through the interference of the Bethe-Heitler process with…
We give an overview of the theory for generalized parton distributions. Topics covered are their general properties and physical interpretation, the possibility to explore the three-dimensional structure of hadrons at parton level, their…