Large momentum transfer electroproduction of mesons

We study the electromagnetic and meson-photon transition form factors of light pseudoscalar mesons from the perturbative QCD (pQCD) approach. In order to include the soft transversal degree of freedom of partons inside hadrons, we introduce the intrinsic transversal momentum distributions (iTMDs), accompanying to the light-cone distribution amplitudes (LCDAs) which depict the longitudinal nonperturbative dynamics of an energetic meson. The main motivations of this work are th...

We study light vector meson photoproduction at small $x$ on the basis of the generalized parton distribution (GPD). Our results on the cross section and spin density matrix elements (SDME) are in fair agreement with DESY experiments

Recent improvements of the hard scattering picture for the large $p_{\perp}$ behaviour of electromagnetic form factors, namely the inclusion of both Sudakov corrections and intrinsic transverse momentum dependence of the hadronic wave function, are reviewed. On account of these improvements the perturbative contributions to the pion's and the nucleon's form factor can be calculated in a theoretically self-consistent way for momentum transfers as low as about $2$ and $3\,{\rm ...

We report the measurement of near threshold neutral pion electroproduction cross sections and the extraction of the associated structure functions on the proton in the kinematic range $Q^2$ from 2 to 4.5 GeV$^2$ and $W$ from 1.08 to 1.16 GeV. These measurements allow us to access the dominant pion-nucleon s-wave multipoles $E_{0+}$ and $S_{0+}$ in the near-threshold region. In the light-cone sum-rule framework (LCSR), these multipoles are related to the generalized form facto...

Advantages of the amplitude method for the vector-meson-production description in respect of the spin-density-matrix-element (SDME) method are discussed. It is shown that for any nonzero amplitudes the angular distribution of final particles is non-negative. The exact formula for $R = \frac{d \sigma_L}{d t}/\frac{d \sigma_T}{d t}$ in terms of the SDMEs for spinless targets and the new approximate formula for nucleons are presented.

The generalized parton distributions (GPDs) of the meson and nucleon at small and large values of the momentum transfer were determined on the basis of the comparative analysis of different sets of experimental data of electromagnetic form factors of the proton and neutron, using the different sets of the parton distribution functions (PDFs). As a result, different form factors of the nucleons and meson were calculated. The t-dependence of these form factors was checked up in...

Electroproduction of light vector mesons is analyzed on the basis of handbag factorization. The required generalized parton distributions are constructed from the CTEQ6 parton distributions with the help of double distributions. The partonic subprocesses are calculated within the modified perturbative approach. The present work extends our previous analysis of the longitudinal cross section to the transverse one and other observables related to both the corresponding amplitud...

In Ultra Relativistic Heavy-Ion Collisions (URHIC's) the light vector mesons play a crucial role in the description of hadronic interactions in a non-pertrubative QCD region. In this region efective hadron models use composite hadrons and mesons as field carriers instead of quarks and gluons. This theoretical review article tries to give a short way of understanding the underlying theory that we have for the conversion of vector mesons into photons together with the so-called...

Recent experimental and theoretical advances in investigating electromagnetic meson production reactions in the nucleon resonance region are reviewed.

We report on numerical studies of the NLO corrections to exclusive meson electroproduction, both in collider and fixed-target kinematics. Corrections are found to be huge at small xB and sizeable at intermediate or large xB.