Colour transparency: A novel test of QCD in nuclear interactions

Abstract

Colour transparency (CT) is a cute and indispensable property of Q C D as a gauge theory. C T tests of Q C D consist of production of the perturbatiue small-sized hadronic state and measuring the strength of its non-perturbatiue diflraction interaction in a nuclear matter. The energy dependence of the final-state interaction in a nuclear matter probes a dynamical evolution from the perturbatiue small-sized state to the full-sized nonperturbatiue hadron. Q C D observables of C T experiments correspond to a novel mechanism of scanning o/ hadronic wauefunctions from the large nonperturbative to the small perturbative size. In these lectures, which are addressed to experimentalists and theorists, I discuss the principle ideas ofCT physics and the physics potential of the hadron and electron facilities in the 1 I5 GeVenergy range. The special effort was made to present the material in the pedagogical and self-consistent way, with an emphasis on the underlying rich quantum-mechanical interference phenomena.

Decisive test of colour transparency in exclusive virtual photoproduction of vector mesons

“…which makes this reaction an ideal laboratory for testing color transparency (CT) ideas (for the recent review on CT see [2,3]). In the exclusive production off nuclei, the nuclear attenuation effects were predicted [1] to be ∝ r 2 Q and vanish at large virtuality Q 2 of the photon, which was confirmed by the recent data on the ρ 0 production from the FNAL E665 experiment [4].…”

“…The cross section σ(r) has the CT property of vanishing at r → 0 [9,10]. Since the CT property is conveniently quantified in terms of σ(r) (for the review see [2,3]), it is important to understand how σ(r) is probed in the exclusive electroproduction.…”

Diffraction driven steep rise of spin structure function gLT=g1+g2 at small x and DIS sum rules

“…1b). Although SCHC diffraction excitation amplitudes are smaller than elastic ones (for suppression of diffraction excitation by the node effect see [30]), the inelastic (p, p * ) spin-flip transitions can be enhanced compared to elastic (p, p ′ ) ones [5]. Consequently, one can not exclude that the contribution of p * excitations would enhance the effective r 5 by a large factor.…”

Erratum: Theoretical interpretation of the NE18 experiment on nuclear transparency inA(e, e′p)scattering

“…It was shown that CT and/or weak final-state interaction (FSI) in A(e, e ′ p) reactions arises from delicate cancellations of contributions from elastic (|i = |p ) and inelastic (|i = |p ) intermediate states |i propagating inside the nucleus [2,3]. At Q 2 ∼ < 7 (GeV/c) 2 the contributions from inelastic rescatterings is still small, however, and hence the very small signal in the NE18 experiment (for a general review on CT see [5][6][7]). Another very interesting aspect of the experiment is the evidence for substantial FSI effects already in the deuteron.…”

“…(2) the factor exp t( b, z)ξ( ∆) in the integrand of Eq. (5) causes a broadening of the p ⊥ -distribution [6,8]:…”