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

We consider exclusive two-pion production in antiproton-deuteron interactions at the beam momenta around 10 GeV/c in the kinematics with large momentum transfer in the underlying hard process $\bar p n \to \pi^- \pi^0$. The calculations are performed taking into account the antiproton and pion soft rescattering on the spectator proton in the framework of the generalized eikonal approximation. We focus on the color transparency effect that is modeled by introducing the depende...

Previous work on color transparency is reviewed briefly with an emphasis on aspects related to an upgrade of CEBAF.

Quantum filtering of the ejectile wave packet from hard $ep$ scattering on bound nucleons puts stringent constraints on the onset of color transparency in $(e,e'p)$ reactions in nuclei at moderate energies. Based on multiple-scattering theory, we derive a novel formula for nuclear transparency and discuss its energy dependence in terms of a color transparency sum rule.

Some experimental results on nuclear transparency effect in pC- and dC-interaction at 4.2 A GeV/c (JINR Dubna) are presented. The "half angle" ({\theta}1/2) technique was used and the particles with emission angle greater and less than {\theta}1/2 are considered separately. The results of the experimental study have been compared with the simulation data coming from the Dubna Cascade model. The values of average multiplicity, average momentum, and average transverse momentum ...

We have studied the diffractive dissociation into di-jets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t_{min} approaches 0) we find that when the per-nucleus cross-section for this process is parameterized as $\sigma = \sigma_0 A^{\alpha}, \alpha$ has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calcul...

We summarize the results of two experimental programs at the Alternating Gradient Synchrotron of BNL to measure the nuclear transparency of nuclei measured in the A(p,2p) quasielastic scattering process near 90 Deg .in the pp center of mass. The incident momenta varied from 5.9 to 14.4 GeV/c, corresponding to 4.8 < Q^2 < 12.7 (GeV/c)^2. First, we describe the measurements with the newer experiment, E850, which had more complete kinematic definition of quasielastic events. In ...

We study the nuclear transparency $T$ for the exclusive reaction $\gamma^*+A\to\rho+p+(A-1)^*$ at incident virtual photon energies $\nu \ge$ 10 GeV %where the final state of the $A-1$-nucleon system is a one-hole state of the initial nucleus, to investigate the separate dependence on the photon virtuality, $Q^2$ and the 4-momentum-transfer-squared to the knocked-out proton, $t$. If the effects of color transparency are included, $T$ shows significant variation with $t$ even f...

Radiation technologies have found wide application in power engineering, medicine, biology and other areas of human activities. However, theoretical calculations of nuclear reactions and, correspondingly, the interpretation of experimental results appear model-dependent. The model-independent calculation of the nuclear reaction must take into account the structure of the nuclear ground state, the final-state nucleon interaction and the contribution of meson exchange currents....

The A-dependence of the quasielastic A(e,e'p) reaction has been studied at SLAC with H-2, C, Fe, and Au nuclei at momentum transfers Q^2 = 1, 3, 5, and 6.8 (GeV/c)^2. We extract the nuclear transparency T(A,Q^2), a measure of the average probability that the struck proton escapes from the nucleus A without interaction. Several calculations predict a significant increase in T with momentum transfer, a phenomenon known as Color Transparency. No significant rise within errors is...

The $\gamma n \to \pi^- p$ and $\gamma p \to \pi^+ n$ reactions are essential probes of the transition from meson-nucleon degrees of freedom to quark-gluon degrees of freedom in exclusive processes. The cross sections of these processes are also advantageous, for the investigation of oscillatory behavior around the quark counting prediction, since they decrease relatively slower with energy compared with other photon-induced processes. In this talk, we discuss recent results ...