Massive Yang-Mills model and diffractive scattering - art. no. 074008

We argue that the massive Yang-Mills model of Kunimasa and Goto, Slavnov, a nd Cornwall, in which massive gauge vector bosons are introduced in a gauge -invariant way without resorting to the Higgs mechanism, may be useful for studying diffractive scattering of strongly interacting particles. With thi s motivation, we perform in this model explicit calculations of S-matrix el ements between quark states, at the tree level, one loop, and two loops, an d discuss issues of renormalizability and unitarity. In particular, it is s hown that the S-matrix element for quark scattering is renormalizable at on e-loop order, and is only logarithmically nonrenormalizable at two loops. T he discrepancies in the ultraviolet regime between the one-loop predictions of this model and those of massless QCD are discussed in detail. In additi on, some of the similarities and differences between the massive Yang-Mills model and theories with a Higgs mechanism are analyzed at the level of the S matrix. Finally, we briefly discuss the high-energy behavior of the lead ing order amplitude for quark-quark elastic scattering in the diffractive r egion. The above analysis sets up the stage for carrying out a systematic c omputation of the higher order corrections to the two-gluon exchange model of the Pomeron using massive gluons inside quantum loops. [S0556-2821(99)04 305-2].