Köln 2004 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 38: Electromagnetic and Hadronic Probes VI
HK 38.5: Vortrag
Donnerstag, 11. März 2004, 15:00–15:15, B
Indication of anomalous exchange in exclusive charmonium photoproduction. — •Alexander Sibirtsev1, Siegfried Krewald1, and Anthony W. Thomas2 — 1IKP-TH, FZJ, Juelich — 2Adelaide University
We find that available data on J/Ψ photoproduction at |t|≥1 GeV are energy independent over the range 22≤√s≤170 GeV and show a very soft t dependence. These results are in striking contradiction with perturbative QCD. Through a systematic analysis of the data we detect a new trajectory, which manifests itself at threshold and is energy independent. The trajectory couples to the axial form factor of the nucleon and can reproduce the J/Ψ exclusive photoproduction data at large -t.
It would be of great interest to study J/Ψ photoproduction at low energies, which should be possible with the operation of HALL D at Jefferson Lab and to clarify whether the forward cross section approaches a value of order 20 nb·GeV−2 starting from threshold.
The contribution from the new trajectory can be investigated experimentally in elastic antiproton-proton scattering at large t that can be done at HESR. The contribution from the new trajectory, which scales as s0 should be well distinguished from the hard scattering processes that scale as s−10. HESR is an unique machine that provides access to large t within large range of s and let us to study the interplay between perturbative and non-perturbative QCD.