The Color Dipole Picture

We give a brief exposition of the color dipole picture of deep inelastic scattering.Comment: Presented at Diffraction 2012, Lanzarote, Canary Islands (Spain), September 10-15, 2012 (Proceedings to appear

Experimental Evidence for Electroweak Corrections Beyond Fermion Loops

We reemphasize the importance of discriminating fermion-loop and bosonic electroweak corrections in the analysis of electroweak precision data. Most recent data are indeed precise enough to require corrections beyond (trivial) fermion loops. An analysis of these data in terms of the observables $\Delta x \equiv \epsilon_{N1} - \epsilon_{N2}$, $\Delta y \equiv - \epsilon_{N2}$ and $\epsilon \equiv - \epsilon_{N3}$ identifies the required additional corrections as vertex corrections at the $W^\pm f\bar f^\prime$ and $Z^0 f\bar f$ vertices. Standard-model values for these corrections are consistent with the experimental data.Comment: Presented at the XXIXth Rencontres de Moriond, March 1994., 4pages uuencoded postscript file, BI-TP 94/1

Vector Meson Dominance

Historically vector-meson physics arose along two different paths to be reviewed in Sections 1 and 2. In Section 3, the phenomenological consequences will be discussed with an emphasis on those aspects of the subject matter relevant in present-day discussions on deep inelastic scattering in the diffraction region of low values of the Bjorken variable.Comment: To appear in the proceedings of "PHOTON2005 International Conference on the Structure and Interactions of the Photon including the 16th International Workshop on Photon-Photon Collisions", Warsaw, 200

Perturbative QCD Evolution and Color Dipole Picture

The proton structure function in the diffraction region of small Bjorken-$x$ and $10 {\rm GeV}^2 \le Q^2 \le 100 {\rm GeV}^2$ behaves as $F_2 (x, Q^2) = F_2 (W^2) = f_0 \cdot (W^2)^{C_2}$, where $x = Q^2 / W^2$. The exponent $C_2$ of the $\gamma^* p$ center-of-mass energy squared, $W^2$, is predicted from evolution of the flavor-singlet quark distribution, $C_2 = 0.29$, and the only free parameter, the normalization $f_0 = 0.063$, is fitted. The evolution of the gluon density multiplied by $\alpha_s (Q^2)$ is dentical to the evolution of the flavor-singlet quark density. This simple picture is at variance with the standard approach to evolution based on the coupled equations of flavor-singlet and gluon density.Comment: 11 pages, 4 figure

The Energy-Dependent Black-Disk Fraction in Proton-Proton Scattering

Recent work by Block et al on the energy-invariant edge in proton-proton scattering is interpreted by quantitatively introducing a energy-dependent black-disk fraction of the proton-proton interaction.Comment: 7 pages, expanded version, including impact-parameter representation and other detail