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

TL;DR

This paper reports precise measurements of CP and CPT symmetry parameters in the neutral kaon system using a large dataset, confirming existing results and placing new limits on possible CPT violation.

Contribution

The study provides the most precise measurements to date of direct CP violation, mass difference, and CPT symmetry parameters in the neutral kaon system using the full KTeV dataset.

Findings

Measured Re(epsilon'/epsilon) = (19.2 ± 2.1) x 10^-4

Determined the KL-KS mass difference as (5270 ± 12) x 10^6 hbar/s

Placed a limit on K0-K0bar mass difference as < 4.8 x 10^-19 GeV/c^2 at 95% C.L.

Abstract

We present precise tests of CP and CPT symmetry based on the full dataset of K to pipi decays collected by the KTeV experiment at Fermi National Accelerator Laboratory during 1996, 1997, and 1999. This dataset contains 16 million K to 2pi0 and 69 million K to pi+pi- decays. We measure the direct CP violation parameter Re(epsilon'/epsilon) = (19.2 pm 2.1)x10-4. We find the KL-KS mass difference Deltam = (5270 pm 12)x10^6 hbar/s and the KS lifetime tauS = (89.62 pm 0.05)x10-12 s. We also measure several parameters that test CPT invariance. We find the difference between the phase of the indirect CP violation parameter, epsilon, and the superweak phase, phi_epsilon - phi_SW = (0.40 pm 0.56) degrees. We measure the difference of the relative phases between the CP violating and CP conserving decay amplitudes for K to pi+pi- (phi+-) and for K to 2pi0 (phi00), Delta phi = (0.30 pm 0.35) degrees. From these phase measurements, we place a limit on the mass difference between K0 and K0bar, DeltaM < 4.8 x 10-19 GeV/c^2 at 95% C.L. These results are consistent with those of other experiments, our own earlier measurements, and CPT symmetry.