Heidelberg 1999 – scientific programme

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T: Teilchenphysik

T 303: Diffraktion 1

T 303.2: Talk

Tuesday, March 16, 1999, 14:15–14:30, TE10

Exclusive production of vector mesons ρ, ρ′ and ρ″ by real and virtual photons — •G. Kulzinger, H.G. Dosch, and H.J. Pirner — Institut für Theoretische Physik der Universität Heidelberg, Philosophenweg 16 & 19, D-69120 Heidelberg

We present a non-perturbative QCD calculation of high-energy diffractive photo- and leptoproduction of vector mesons ρ, ρ′ and ρ″ on a nucleon, cf. Refs. [1,2]. The initial photon splits up in a qq-dipole and transforms into a vector meson by scattering on the quark-diquark nucleon. The dipole-dipole scattering amplitude is provided by the non-perturbative model of the stochastic QCD vacuum, the wave functions result from considerations on the light-cone. We assume the physical ρ′- and ρ″-states to be mixed states of an active 2S-excitation and an inert rest whose coupling to the photon is suppressed. We obtain good agreement with the experimental data and get an understanding of the markedly different spectrum in the π⁺π⁻-invariant mass for photoproduction and e⁺e⁻-annihilation.

[1] G. Kulzinger, H.G. Dosch und H.J. Pirner, hep-ph/9806352: Diffractive photo- and leptoproduction of vector mesons ρ, ρ′ and ρ″, accepted for publication in Eur.Phys.J.C (1998).

[2] G. Kulzinger, hep-ph/9808440: Exclusive production of vector mesons ρ, ρ′ and ρ″ by real and virtual photons, to be published in Nucl.Phys.B (Proc.Suppl.).