Group independent color decomposition of next-to-leading order matrix elements for e^+ e^- \to four partons

Abstract

We present the next-to-leading order partonic cross sections involving an electroweak vector boson and four massless partons (quarks, gluons or long living gluinos) in a general gauge theory with a simple Lie Group. The vector boson couples to a massless lepton pair and a quark-antiquark pair. The cross sections are given in terms of group independent kinematical functions multiplying the eigenvalues of the Casimir operators of the Lie group. This kind of color decomposition is required for the calculation of O($α_s^3$) corrections to the group independent kinematical functions in the four-jet production cross sections in electron-positron annihilation. The knowledge of these corrections facilitates the simultaneous precision meaurement of the strong coupling and the color charge factors using the four-jet LEP or SLC data as well as the test whether these data favour or exclude the existence of a light gluino.