Light Cone Physics and Quark Parton Model.

Light cone field theory is a very useful tool for calculations involving high energy processes. In addition, the light cone frame is the natural frame for the parton model. However, field theory quantized in a light cone frame has certain unfamiliar problems associated with the choice of the light cone gauge. The use of the light cone theory in perturbative calculations contains a certain type of singularities. This occurs in attempts to write a bound-state equation. By getting the light cone bound -state equation from the Bethe-Salpeter equation, which is free from this kind of problem, we are able to examine the singularities in the light cone calculations and fix the problem. Applications of the light cone parton model are successful in describing hadronic interactions. We will illustrate this in the four-jet productions by double parton scattering. To do this, we start with a Bethe-Salpeter wave function in the expression of the scattering cross section. By using the relation of the Bethe-Salpeter wave function and the light cone wave function, we can express the cross section in terms of the light cone wave function. The resulting picture is that the hadron scattering can be viewed as interactions among partons. The calculation is simpler and more intuitive than using the traditional method. The result will be used to compare with the data of four-jet events from single parton scattering.