Appendix A

Three-jet Kinematics

We define the momenta for three-jet production as in fig. 4, and work, as always, in the N center of mass system. We take to be the c.m.s. energy in the N collision, so that (ignoring the proton mass)

[ Figure 4 ] The kinematics of three-jet production in N collisions. 1 is the initial parton; 2 the initial while 3 and 4 are the final state partons. The final state ``diquark'' (fragments of the nucleon) is not labeled in the figure.

For the subprocess, we define the kinematic invariants

and we take the angle between and the direction to be . is the fraction of the nucleon's momentum carried by the incoming parton . We assume here that has no component transverse to . Then one finds

and are obtained by replacing in eq. (A.3) with . In the limit , (A.3) reduces to

The energy of the remnants of the nucleon (`diquark') after the ejection of momentum is

The fractional energies of the three final particles (which are all taken to be massless) are therefore:

In terms of these, one finds, for example,

For , this becomes , and for ,

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