Plasma measurements conducted in the vincinity of Venus on the spacecraft VENERA-4

Plasma flux measurements in vicinity of Venus by charged particle traps on Venera-4 spacecraf

Comparison of Certain Results of Simultaneous Measurements of Solar Wind Characteristics on Spacecrafts ''Venera-3'' and ''Pioneer-6''

Ion concentration, ion velocity, and other solar wind characteristics measured simultaneously aboard spacecraf

Signs of crossing by the moon of the earth's magnetosphere tail according to data of charged particle traps on the first artificial satellite of the moon /Luna-10/

Space probe charged particle data evidence for moon crossing of Earth magnetospheric tai

Off-forward parton distributions and Shuvaev's transformations

We review Shuvaev's transformations, that relate off-forward parton distributions (OFPDs) to so-called effective forward parton distributions (EFPDs). The latter evolve like conventional forward partons. We express nonforward amplitudes, depending on OFPDs, directly in terms of EFPDs and construct a model for the EFPDs, which allows to consistently express them in terms of the conventional forward parton distributions and nucleon form factors. Our model is self-consistent for arbitrary x, xi, mu, and t.Comment: 13 pages, 7 eps-figures, LaTeX2e, added references, corrected typo

Regge Behavior of DIS Structure Functions

Building on previous works of the mid 1960's, we construct an integral equation for forward elastic scattering (t=0) at arbitrary virtuality Q^2 and large s=W^2. This equation sums the ladder production of massless intermediate bosons to all orders, and the solution exhibits Regge behavior. The equation is used to study scattering in a simple chi^2 phi scalar theory, where it is solved appoximately and applied to the study of DIS at small x. We find that the model can naturally describe the quark distribution in both the large x region and the small x region dominated by Reggeon exchange.Comment: 13 pages with 5 figure

Unbiased analysis of CLEO data at NLO and pion distribution amplitude

We discuss different QCD approaches to calculate the form factor F^{\gamma^*\gamma\pi}(Q^2) of the \gamma^*\gamma\to\pi^{0} transition giving preference to the light-cone QCD sum rules (LCSR) approach as being the most adequate. In this context we revise the previous analysis of the CLEO experimental data on F^{\gamma^*\gamma\pi}(Q^{2}) by Schmedding and Yakovlev. Special attention is paid to the sensitivity of the results to the (strong radiative) \alpha_s-corrections and to the value of the twist-four coupling \delta^2. We present a full analysis of the CLEO data at the NLO level of LCSRs, focusing particular attention to the extraction of the relevant parameters to determine the pion distribution amplitude, i.e., the Gegenbauer coefficients a_2 and a_4. Our analysis confirms our previous results and also the main findings of Schmedding and Yakovlev: both the asymptotic, as well as the Chernyak--Zhitnitsky pion distribution amplitudes are completely excluded by the CLEO data. A novelty of our approach is to use the CLEO data as a means of determining the value of the QCD vacuum non-locality parameter \lambda^2_q = / =0.4 GeV^2, which specifies the average virtuality of the vacuum quarks.Comment: 25 pages, 5 figures, 4 tables; format and margins corrected to fit page size; small changes in the text and correction of misprint

Skewed parton distributions and the scale dependence of the transverse size parameter

We discuss the scale dependence of a skewed parton distribution of the pion obtained from a generalized light-cone wave function overlap formula. Using a simple ansatz for the transverse momentum dependence of the light-cone wave function and restricting ourselves to the case of a zero skewedness parameter, the skewed parton distribution can be expressed through an ordinary parton distribution multiplied by an exponential function. Matching the generalized and ordinary DGLAP evolution equations of the skewed and ordinary parton distributions, respectively, we derive a constraint for the scale dependence of the transverse size parameter, which describes the width of the pion wave function in transverse momentum space. This constraint has implications for the Fock state probability and valence distribution. We apply our results to the pion form factor.Comment: 10 pages, 4 figures; version to appear in Phys. Rev. D; Refs. added, new discussion of results for pion form factor in view of new dat

Hard exclusive processes and higher-order QCD corrections

The short review of the higher order corrections to the hard exclusive processes is given. Different approaches are discussed and the importance of higher-order calculations is stressed.Comment: 17 pages; talk given at the 9th Adriatic Meeting, Dubrovnik 200

Form Factors and QCD in Spacelike and Timelike Region

We analyze the basic hard exclusive processes: \pi\gamma*\gamma - transition, pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q^2<0 to the timelike region q^2 >0 of the relevant momentum transfers. We describe the construction of the timelike version of the coupling constant \alpha_s. We show that due to the analytic continuation of the collinear logarithms each eigenfunction of the evolution equation acqiures a phase factor and investigate the resulting interference effects which are shown to be very small. We found no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, we use a QCD sum rule inspired model and show that there are non-canceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region.Comment: 12 pages, LaTeX; a few typos corrected, references adde

DVCS amplitude at tree level: Transversality, twist-3, and factorization

We study the virtual Compton amplitude in the generalized Bjorken region (q^2 -> Infinity, t small) in QCD by means of a light-cone expansion of the product of e.m. currents in string operators in coordinate space. Electromagnetic gauge invariance (transversality) is maintained by including in addition to the twist-2 operators 'kinematical' twist-3 operators which appear as total derivatives of twist-2 operators. The non-forward matrix elements of the elementary twist-2 operators are parametrized in terms of two-variable spectral functions (double distributions), from which twist-2 and 3 skewed distributions are obtained through reduction formulas. Our approach is equivalent to a Wandzura-Wilczek type approximation for the twist-3 skewed distributions. The resulting Compton amplitude is manifestly transverse up to terms of order t/q^2. We find that in this approximation the tensor amplitude for longitudinal polarization of the virtual photon is finite, while the one for transverse polarization contains a divergence already at tree level. However, this divergence has zero projection on the polarization vector of the final photon, so that the physical helicity amplitudes are finite.Comment: 34 pages, revtex, 1 eps figure included using epsf. Misprints corrected, one reference adde