Nuclear Transparency with the gamma + n -> pi- + p Process in 4He

We use a semi-classical approximation to investigate the effects of color transparency on pion electroproduction reactions. The resulting reduced nuclear interactions produce significant, but not dominating, differences with the results of conventional distorted-wave, Glauber-type treatments at kinematics accessible to Jefferson Laboratory. Nuclear effects that could mimic the influence of color transparency are also discussed.

This paper presents, for the first time, measurements of neutron transparency ratios for nuclei relative to C measured using the (e,e'n) reaction, spanning measured neutron momenta of 1.4 to 2.4 GeV/c. The transparency ratios were extracted in two kinematical regions, corresponding to knockout of mean-field nucleons and to the breakup of Short-Range Correlated nucleon pairs. The extracted neutron transparency ratios are consistent with each other for the two measured kinemati...

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.

The nuclear transparency and the distorted momentum distributions of 4He in the semi-inclusive process 4He(e,e'p)X are calculated within the Glauber multiple scattering approach using for the first time realistic four-body variational wave functions embodying central and non-central nucleon-nucleon (N-N) correlations. The contributions from N-N correlations and from Glauber multiple scattering are taken into account exactly to all orders. It is shown that non-central correlat...

In light of the recent Jefferson Laboratory (JLab) data for the nuclear $^{12}\text{C}(e,e'p)$ transparencies, calculations, obtained in a relativistic multiple scattering Glauber approximation, are discussed. The shell-separated $^{12}$C transparencies are shown and it is concluded that the $p$-shell nucleons are 75\% more transparent than the $s$-shell ones. The presented comparisons between the calculations made here and the current $^{12}\text{C}(e,e'p)$ data show no clea...

The spectral function, measured in $A(e,e'p)$ reactions, is distorted by the final-state interaction of the struck proton with the residual nucleus. This causes a broadening of the observed transverse-momentum distribution which is large even in the $d(e,e'p)$ reaction. We discuss the effects of this $p_{\perp}$-broadening on the nuclear transparency measured in the recent NE18 experiment. Within conventional Glauber theory we can describe the measurements. Transparency effec...

The energy dependence of $90^o$ $cm$ fixed angle scattering of $\pi p \to \pi' p'$ and $\gamma p\to \pi^+ n$ at large momentum transfer are found to be well described in terms of interfering short and long distance amplitudes with dynamical phases induced by Sudakov effects. We calculate the color transparency ratio for the corresponding processes in nuclear environments $\pi A\to \pi'p(A-1)$ and $\gamma A\to \pi N (A-1)$ taking nuclear filtering into account. A prediction th...

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 ...

Color Transparency refers to the vanishing of the hadron-nucleon interaction for hadrons produced inside a nucleus in high momentum exclusive processes. We briefly review the concept behind this unique Quantum Chromo Dynamics' phenomenon, the experimental search for its onset and the recent progress made at intermediate energies.

Cross sections for the p($e,e'\pi^{+}$)n process on $^1$H, $^2$H, $^{12}$C, $^{27}$Al, $^{63}$Cu and $^{197}$Au targets were measured at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in order to extract the nuclear transparencies. Data were taken for four-momentum transfers ranging from $Q^2$=1.1 to 4.8 GeV$^2$ for a fixed center of mass energy of $W$=2.14 GeV. The ratio of $\sigma_L$ and $\sigma_T$ was extracted from the measured cross sections for $^1$H...