KTeV Results: Re($\epsilon' / \epsilon$) and Rare Decay Results

TL;DR

This paper reports precise measurements of direct CP violation in kaon decays, kaon parameters, and rare decay branching fractions based on Fermilab data from 1996-1999, advancing understanding of kaon physics.

Contribution

It provides new, high-precision measurements of Re(ε'/ε), kaon parameters, and rare decay branching fractions from the KTeV experiment data.

Findings

Precise value of Re(ε'/ε) measured.

Determined kaon parameters τ_S, Δm, φ_{+-}, Δφ.

Measured branching fraction of K_L → e^+ e^- μ^+ μ^-.

Abstract

The KTeV physics program encompasses many goals including a precision measurement of the direct CP violation parameter Re($\epsilon' / \epsilon$) in $K \to \pi \pi$ decays, and studies of rare neutral kaon decays. The KTeV detector collected data during the Fermilab fixed-targed runs of 1996-97 and 1999. This article focuses on the precision measurement of the direct CP violation parameter Re($\epsilon' / \epsilon$) using the 1996-97 data set. In addition, measurements of the neutral kaon parameters $\tau_S$, $\Delta m$, $\phi_{+-}$, $\Delta \phi$ from that data set and a new measurement of the branching fraction of $K_L \to e^+ e^- \mu^+ \mu^-$ from the 1997 and 1999 data also are presented.