Oscillating Color Transparency in $\pi A\to \pi p (A-1)$ and $\gamma A\to \pi N (A-1)$

The current status of the theory of and the experimental evidence for color transparency are reviewed. The problems with interpretation of quasielastic scattering on nuclei are discussed to some detail.

The quasielastic (e,e$^\prime$p) reaction was studied on targets of deuterium, carbon, and iron up to a value of momentum transfer $Q^2$ of 8.1 (GeV/c)$^2$. A nuclear transparency was determined by comparing the data to calculations in the Plane-Wave Impulse Approximation. The dependence of the nuclear transparency on $Q^2$ and the mass number $A$ was investigated in a search for the onset of the Color Transparency phenomenon. We find no evidence for the onset of Color Transp...

The physics observables dedicated to the study of color transparency are diverse. After a brief pedagogical introduction, we emphasize the complementarity of the nuclear filtering and color transparency concepts. The importance of quantum interferences leads to suspect pictures based on the preparation of a squeezed state of small transverse size leading to a rapid transverse expansion. The different roles of heavy and light nuclei are emphasized. The possibility of color tra...

The process $\pi + A$ leading to a pair of mini-jets at high relative transverse momentum ($k_t \gsim 2$ GeV) while leaving the nucleus in its ground state was selected as a definitive test of the existence of color transparency by Frankfurt, Miller and Strikman in 1993. The preliminary results of Fermilab experiment E791, led by Ashery and Weiss-Babai, show a strong A-dependence, consistent with the notion of color transparency.

Efforts to observe color transparency in the reactions: (e,e'p), (p,pp) and coherent nuclear diffractive dissociation of pions into two jets are reviewed.

We introduce a data analysis procedure for color transparency experiments which is considerably less model dependent than the transparency ratio method. The new method is based on fitting the shape of the A dependence of the nuclear cross section at fixed momentum transfer to determine the effective attenuation cross section for hadrons propagating through the nucleus. The hard scattering cross section is then determined directly from the data. We apply this procedure to the ...

We review the perturbative QCD formalism of hadronic electromagnetic form factors and the color transparency ratio for quasi-exclusive electroproduction of the proton and pion from nuclear targets. We have completed the first full calculations including all leading order quark subprocesses and integrations over distribution amplitudes, including Sudakov effects. For the case of the proton, the calculated result shows scaling beyond $Q^2=10$ GeV$^2$. The calculation incorporat...

We examine the nuclear transparency for the quasi-elastic ($e, e'p$) process at large momentum transfers in a relativistic quantum-mechanical model for the internal structure of the proton, using a relativistic harmonic oscillator model. A proton in a nuclear target is struck by the incident electron and then propagates through the residual nucleus suffering from soft interactions with other nucleons. We call the proton "dynamical" when we take into account of internal excita...

Nuclear transparency in pion-induced nuclear reactions has been investigated based on Glauber multiple scattering theory considering a two-step process within the framework of vector meson dominance (VMD). In the present context, the application of the quantum diffusion model (QDM) to the Glauber theory plays a role in explaining the dependence of the transparency on the four-momentum transfer squared $Q^2$. The short-range correlation (SRC) considered further gives the contr...

CONTENTS. 1.Introduction, 1.1 QCD ideas to be tested; 2. Coherence phenomena in QED, 2.1 Charge transparency, 2.2 Charge filtering, 2.3 Charge opacity; 3. Color transparency in perturbative QCD, 3.1 Coherence length in QCD, 3.2 Bjorken scaling for deep inelastic processes, 3.3 Hard Coherent Diffraction {}From Nucleons and Nuclei; 4. Soft Diffractive Physics and Color Fluctuations, 4.1 Scattering eigenstates formalism; 4.2 Current information on color fluctuations in Hadrons, ...