Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System

TL;DR

This paper reports precise measurements of CP violation, CPT symmetry, and other parameters in the neutral kaon system, confirming CPT invariance and providing updated values for key kaon decay parameters.

Contribution

First precise measurement of direct CP violation parameter Re(e'/e) and CPT symmetry tests in neutral kaon decays using 1996-1997 data from the KTeV experiment.

Findings

Re(e'/e) = (20.7 +- 2.8) x 10^-4

Phase difference Delta-phi = (+0.39 +- 0.50) degrees, consistent with CPT symmetry

KL-KS mass difference and KS lifetime measured with high precision

Abstract

We present a series of measurements based on K -> pi+pi- and K -> pi0pi0 decays collected in 1996-1997 by the KTeV experiment (E832) at Fermilab. We compare these four K -> pipi decay rates to measure the direct CP violation parameter Re(e'/e) = (20.7 +- 2.8) x 10^-4. We also test CPT symmetry by measuring the relative phase between the CP violating and CP conserving decay amplitudes for K->pi+pi- (phi+-) and for K -> pi0pi0 (phi00). We find the difference between the relative phases to be Delta-phi = phi00 - phi+- = (+0.39 +- 0.50) degrees and the deviation of phi+- from the superweak phase to be phi+- - phi_SW =(+0.61 +- 1.19) degrees; both results are consistent with CPT symmetry. In addition, we present new measurements of the KL-KS mass difference and KS lifetime: Delta-m = (5261 +- 15) x 10^6 hbar/s and tauS = (89.65 +- 0.07) x 10^-12 s.