ABSTRACT
This chapter considers what happens at higher energy – in particular from 5 to 18 GeV. The analysis directly by sums of resonances is hopeless as too many are involved. The chapter discusses a very small fraction of the total photon nucleon cross section at high energy. In Kegge theory the exchange of a trajectory can be interpreted as a sum over t channel resonances. In each case the polarization of the exchanged resonance is used up in getting as high a power of s as possible, by being in the direction of the two longitudinal momenta. The photon comes in with polarization e¯ in plane of sheet, if this is reflected in a mirror in the plane of scattering everything looks the same except that since there is a pseudoscalar particle the amplitude changes sign, it is therefore zero.
