The perturbative odderon in elastic pp and pp̄ scattering

The evidence for the existance of an odderon [1] remains scarce. To date, the best evidence comes from the differential cross section in elastic pp and pp̄ scattering. The pp data show a dip structure at −t ≈ 1.3 GeV while the pp̄ data only flatten off at that point. The odderon, being odd under charge conjugation, couples with different signs to protons and antiprotons and can hence account for that difference. We describe the odderon in leading order perturbation theory, as a perturbative three-gluon exchange in a C = −1 state. We assume that the scale 1.3 GeV is large enough for perturbation theory to be valid; and we do no log s resummation. We consider three different models for the odderon-proton coupling: one proposed by Fukugita and Kwieciński, one proposed by Levin and Ryskin and a geometrical model which allows an estimation of the size of a possible diquark cluster in the proton.