Absorption in High-Energy Photoproduction

Absorption in high-energy photoproduction has been derived using a Regge amplitude. It is found that this depends strongly on the square of the four-momentum transfer t, smaller values of $|t|$ giving much less absorption. This behavior differs markedly from that of the Drell peripheral model with a constant absorption factor. The absorption is calculated for s and t values corresponding to energies encountered in a recent SLAC experiment, and is seen to reduce the cross section by factors of 1/220 to 1/25, depending on t. Factors of this order are needed to bring experiment and theory into agreement. The high-energy asymptotic behavior of the amplitude with absorption is found to differ from the usual Regge behavior. The usual absorption using a Born amplitude is also elaborated and generalized and is compared with recent DESY data. The well-known high-energy Regge behavior of the cross section without absorption, dσdt=C(t)s^2α(t)-2, is derived for all spins in an Appendix.