The precise determination of Re(epsilon'/epsilon)

Abstract

CP violation in the neutral kaon system is known to be dominated by the mixing of K0 and anti-K0. Direct CP violation in the 2 pion decays of neutral kaons has been a controversial subject over the last decade. A strong experimental effort has been devoted to the precise measurement of the direct CP violation parameter re(epsilon'/epsilon). After 10 years of detector development, data collection and analysis, the NA48 experiment at CERN and the KTeV experiment at Fermilab have now established direct CP violation as a fact. Both KTeV and NA48 use the same experimental principle, measuring the double ratio of long lived and short lived neutral kaons to two charged and two neutral pions. However, their experimental and analysis techniques differ in important ways, and I will extensively discuss the two approaches. I will also present the latest results on epsilon'/epsilon from both experiments, which were announced just a few months ago.