FIRST RADIOCARBON RESULTS OF ONEGA LAKE BOTTOM SEDIMENTS BASED ON CONVENTIONAL AND AMS METHODS

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DVCS on the nucleon : study of the twist-3 effects

We estimate the size of the twist-3 effects on deeply virtual Compton scattering (DVCS) observables, in the Wandzura-Wilczek approximation. We present results in the valence region for the DVCS cross sections, charge asymmetries and single spin asymmetries, to twist-3 accuracy.Comment: 20 pages, 6 figure

Effective chiral lagrangian in the chiral limit from the instanton vacuum

We study the effective chiral Lagrangian in the chiral limit from the instanton vacuum. Starting from the nonlocal effective chiral action, we derive the effective chiral Lagrangian, using the derivative expansion to order $O(p^4)$ in the chiral limit. The low energy constants, $L_1$, $L_2$, and $L_3$ are determined and compared with various models and the corresponding empirical data. The results are in a good agreement with the data. We also discuss about the upper limit of the sigma meson, based on the present results.Comment: 14 pages, 5 figures, submitted to Phys.Rev.

Pedagogic model for Deeply Virtual Compton Scattering with quark-hadron duality

We show how quark-hadron duality can emerge for valence spin averaged structure functions, and for the non-forward distributions of Deeply Virtual Compton Scattering. Novel factorisations of the non-forward amplitudes are proposed. Some implications for large angle scattering and deviations from the quark counting rules are illustrated.Comment: Version accepted by Phys. Rev.

Hard exclusive pseudoscalar meson electroproduction and spin structure of a nucleon

The amplitude for hard exclusive pseudoscalar meson electroproduction off nucleon (nuclear) targets is computed in QCD within the leading $\alpha_s \ln {Q^2/\lambda_{QCD}^{2}}$ approximation. We show that the distribution of recoil nucleons depends strongly on the angle between the momentum of the recoil nucleon and the polarization vector of the target (or outgoing nucleon). This dependence is especially sensitive to the spin flip skewed parton distribution (SPD) $\widetilde E$. We argue also that the scaling for this spin asymmetry sets in at lower Q^2 than that for the absolute cross section. Basing on the chiral quark-soliton model of the nucleon we estimate quantitatively the spin asymmetry. In the case of pi+ production this asymmetry is dominated at small t by the contribution of the pion pole in the isovector SPD $\widetilde E$ as required by PCAC. In the case of K0 production off a proton we find a large enhancement of the cross section as compared to the case of pi0 production. For the forward production of neutral pseudoscalar mesons off a deuteron target we find the cross section should be zero for the zero deuteron helicity (along the $\gamma^*D$ direction). We consider also cross sections of quasielastic processes off nuclei including the feasibility to implant K+,rho-mesons into nuclear volume.Comment: 19 pages, one figur

Exploring skewed parton distributions with two body models on the light front II: covariant Bethe-Salpeter approach

We explore skewed parton distributions for two-body, light-front wave functions. In order to access all kinematical regimes, we adopt a covariant Bethe-Salpeter approach, which makes use of the underlying equation of motion (here the Weinberg equation) and its Green's function. Such an approach allows for the consistent treatment of the non-wave function vertex (but rules out the case of phenomenological wave functions derived from ad hoc potentials). Our investigation centers around checking internal consistency by demonstrating time-reversal invariance and continuity between valence and non-valence regimes. We derive our expressions by assuming the effective qq potential is independent of the mass squared, and verify the sum rule in a non-relativistic approximation in which the potential is energy independent. We consider bare-coupling as well as interacting skewed parton distributions and develop approximations for the Green's function which preserve the general properties of these distributions. Lastly we apply our approach to time-like form factors and find similar expressions for the related generalized distribution amplitudes.Comment: 25 pages, 12 figures, revised (minor changes but essential to consistency

The chirally-odd twist-3 distribution function e(x) in the chiral quark-soliton model

The chirally-odd twist-3 nucleon distribution e(x) is studied in the large-Nc limit in the framework of the chiral quark-soliton model at a low normalization point of about 0.6 GeV. The remarkable result is that in the model e(x) contains a delta-function-type singularity at x=0. The regular part of e(x) is found to be sizeable at the low scale of the model and in qualitative agreement with bag model calculations.Comment: 16 pages, 6 figures, revtex, Ref.[50] and footnote 3 adde

Quark Imaging in the Proton Via Quantum Phase-Space Distributions

We develop the concept of quantum phase-space (Wigner) distributions for quarks and gluons in the proton. To appreciate their physical content, we analyze the contraints from special relativity on the interpretation of elastic form factors, and examine the physics of the Feynman parton distributions in the proton's rest frame. We relate the quark Wigner functions to the transverse-momentum dependent parton distributions and generalized parton distributions, emphasizing the physical role of the skewness parameter. We show that the Wigner functions allow to visualize quantum quarks and gluons using the language of the classical phase space. We present two examples of the quark Wigner distributions and point out some model-independent features.Comment: 20 pages with 3 fiture

Transversity Form Factors and Generalized Parton Distributions of the pion in chiral quark models

The transversity Generalized Parton Distributions (tGPDs) and related transversity form factors of the pion are evaluated in chiral quark models, both local (Nambu--Jona-Lasinio) and nonlocal, involving a momentum-dependent quark mass. The obtained tGPDs satisfy all a priori formal requirements, such as the proper support, normalization, and polynomiality. We evaluate generalized transversity form factors accessible from the recent lattice QCD calculations. These form factors, after the necessary QCD evolution, agree very well with the lattice data, confirming the fact that the spontaneously broken chiral symmetry governs the structure of the pion also in the case of the transversity observables.Comment: 6 pages, 3 figures, presented by WB at LIGHTCONE 2011, 23 - 27 May, 2011, Dalla

FIRST RADIOCARBON RESULTS OF ONEGA LAKE BOTTOM SEDIMENTS BASED ON CONVENTIONAL AND AMS METHODS

48-5