Observation of Direct CP Violation in K_{S,L} to \pi \pi Decays

TL;DR

This paper reports the first definitive observation of direct CP violation in K meson decays, measuring the parameter Re(ε'/ε) with high precision, confirming a fundamental asymmetry in particle physics.

Contribution

The paper provides the first clear measurement of direct CP violation in K decays, establishing CP violation in decay processes with improved experimental accuracy.

Findings

Re(ε'/ε) = (28.0 ± 3.0 (stat) ± 2.8 (syst)) × 10^{-4}

Confirmed the existence of direct CP violation in K decays

Provided high-precision experimental evidence for CP asymmetry

Abstract

We have compared the decay rates of K_L and K_S to \pi^+ \pi^- and \pi^0 \pi^0 final states using a subset of the data from the KTeV experiment (E832) at Fermilab. We find that the direct-CP-violation parameter Re(\epsilon'/\epsilon) is equal to (28.0 \pm 3.0 (stat) \pm 2.8 (syst)) \times 10^{-4}. This result definitively establishes the existence of CP violation in a decay process.