Distributions in Four-Fermion Processes

Abstract

The programs WPHACT and WTO, which are designed for computing cross sections and other relevant observables in the $e^+e^-$ annihilation into four fermions, are used to make detailed and complete predictions for the semi-leptonic and fully hadronic channels $e^+e^- \to \barq q lν, \barq q \barq q$. Both the total cross sections in the LEP~2 energy range and some of the most relevant distributions are analyzed. Particular algorithms are introduced for the fully hadronic channels in order to analyze the $WW$ physics and to properly define the signal versus the background. With appropriate kinematical cuts it has been shown that the Neutral Current background can be made vanishingly small when the problem of determining the $W$ boson mass is addressed. The remaining background from the complete Charge Current and Mixed processes is again small but not completely negligible. A detailed discussion is performed on the validity of the most relevant approximations such as the double-resonant one. The inclusion of final state QCD correction, in its {\it naive} form (NQCD), is discussed and various implementations are examined.