Prof John Cardy FRS

Abstract:

We present a consistent picture of a pomeron pole with intercept one, together with its cuts, which evades the decoupling arguments. We use the reggeon cut discontinuity formulae to introduce Gribov's reggeon calculus as an exact solution of multiparticle t-channel unitarity. We show how, within the calculus, two-pomeron iterations of a singular kernel can be responsible for the zero in the triple-pomeron vertex. Using the concept of a bare pomeron pole as a multiperipheral production process which is subsequently renormalised by other effects, we apply the reggeon calculus analysis to inclusive cross sections. We find that the inclusive sum rule decoupling arguments are avoided because of the addition of enhanced absorptive corrections to the conventional Regge pole contributions. However, we show that in this picture the combined pole and two-pomeron cut contribution to the total cross section factories to order (ln s)^-2. We also show that, when the correct helicity structure of the pomeron is taken into account, the s-channel unitarity condition for pomeron scattering amplitudes does not lead to any serious decouplings. © 1974.

Abstract:

It is shown how, in the weak coupling solution of the reggeon calculus, pomeron amplitudes acquire zeros when all the pomerons have zero mass, in a manner similar to that of the triple-pomeron coupling. This latter zero is found to have a trajectory away from t = 0 equal to that of the two-pomeron cut. The weak coupling solution is shown to be equivalent to the theory being asymptotically free in the infrared region. © 1974.

Abstract:

We show that when final state interactions are added to the parton model Drell-Yan formula for massive lepton pair production, they do not change the cross section. © 1974.

Abstract:

We discuss some general properties of the reggeon calculus with input intercept greater than one, in an attempt to formulate a model yielding indefinitely rising cross sections which is consistent with t-channel unitarity. In general the leading behaviour of the amplitude always factorises. If interactions between reggeons are ignored the scattering is equivalent to that from a grey absorbing disk of radius O (ln s). Diagrams involving such interactions are subject to large-scale cancellations. These enable the model to give sensible results for inclusive cross sections. In quantum number exchange reactions, factorisation of the Regge pole residues is weakly broken in the model. © 1974.