Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

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.