Virtual Compton Scattering on the Proton at High s and Low t

Virtual Compton Scattering (VCS) at low transferred momenta to the proton ($t$) and sufficiently high c.m. energies ($s$) may be used to a) study $Q^2$--dependence of leading $t$--channel exchanges and b) look for onset of scaling behavior with increasing $Q^2$. I discuss the implications for perturbative and nonperturbative QCD and suggest possible experiments.Comment: LaTeX, 7 pages, 3 figures, requires sprocl.sty, psfig.st

Magnetic Radius of the Deuteron

The root-mean square radius of the deuteron magnetic moment distribution, $r_{Md}$, is calculated for several realistic models of the $NN$--interaction. For the Paris potential the result is $r_{Md} = 2.312 \pm 0.010$ fm. The dependence of $r_{Md}$ on the choice of $NN$ model, relativistic effects and meson exchange currents is investigated. The experimental value of $r_{Md}$ is also considered. The necessity of new precise measurements of the deuteron magnetic form factor at low values of $Q^2$ is stressed.Comment: 4 pages, RevTe

Relativistic Charge Form Factor of the Deuteron

Relativistic integral representation in terms of experimental neutron-proton scattering phase shifts alone is used to compute the charge form factor of the deuteron $G_{Cd}(Q^2)$. The results of numerical calculations of $|G_{Cd}(Q^2)|$ are presented in the interval of the four-momentum transfers squared $0 \leq Q^2 \leq 35 fm^{-2}$. Zero and the prominent secondary maximum in $|G_{Cd}(Q^2)|$ are the direct consequences of the change of sign in the experimental $^3S_1$- phase shifts. Till the point $Q^2 \simeq 20 fm^{-2}$ the total relativistic correction to $|G_{Cd}(Q^2)|$ is positive and reaches the maximal value of 25% at $Q^2 \simeq 14 fm^{-2}$.Comment: 9 pages, LaTeX, 2 postscript figures, uses wor-sci.sty, epsf.st

Interplay of Hard and Soft Processes at JLab Energies

Even at moderate energy machines, there is a regime where hard pion electroproduction proceeds by a perturbatively calculable process. The process, we claim, is not the leading twist fragmentation one but rather a higher twist process that produces kinematically isolated pions. Semiexclusive data may teach us more about parton distribution functions of the target and the pion distribution amplitude. In addition, there is a connection to generalized parton distribution calculations of exclusive processes in that the perturbative kernel is the same.Comment: 8 pages, 9 figures, Written version of invited talk by CEC at the Second International Symposium on the Gerasimov-Drell-Hearn sum rule and the spin structure of the nucleon (GDH2002), Genoa, Italy, 3--6 July 2002, and of talk by CEC under the title ``Hard Pion Electroproduction at Medium Energies'' at the XVI International Conference on Particles and Nuclei (PANIC02), Osaka, Japan, 30 September--4 October 2002 [WM-02-111; JLAB-THY-02-62

Form Factors of Kaon Semileptonic Decays

A calculation of the semi--leptonic decays of the kaon ($K_{l3}$) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for $K_{l3}$ are predicted with absolutely no parameter adjustments of the model. We obtained for the form factor parameters: $f_-(q^2=m_l^2)/f_+(q^2=m_l^2)=-0.28$ and $\lambda_+$= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.Comment: LaTeX, 3 pages, no figures, requires sprocl.st