New Directions in Kaon Physics

TL;DR

Recent kaon decay measurements are advancing understanding of fundamental symmetries and CKM matrix elements, with ongoing and planned experiments aiming for high-precision results to test the Standard Model.

Contribution

The paper reviews recent experimental progress and outlines future plans for high-precision kaon decay measurements related to CKM unitarity and discrete symmetries.

Findings

New measurements inform CKM unitarity tests.

Experiments aim to observe ~100 events of rare kaon decays.

Future experiments target ~1000 events for precise analysis.

Abstract

Recent measurements of kaon decays provide new information about CKM unitarity, lepton universality, and discrete symmetries. KLOE-2, the proposed extension of the kaon physics program at Frascati, will extend the world data set on kaon decays and conduct interference measurements with neutral kaons. Meanwhile, the decays K \to \pi\nu\bar{\nu} can be directly related to the CKM matrix elements with minimal theoretical uncertainty, and are the focus of a series of experiments. Several events of K+ \to \pi+\nu\bar{\nu} have been observed to date; the goal of the NA62 experiment at CERN is to perform an O(100)-event measurement in this channel. Initiatives in Japan--the E391a experiment at KEK, to become E14 at J-PARC--are focused on collecting a few KL \to \pi0\nu\bar{\nu} events in a first step, while working towards an O(100)-event measurement. Experiments capable of performing O(1000)-event measurements in both channels have been discussed.