A direct test of time-reversal symmetry in the neutralKmeson system withKS→πℓνandKL→ 3π0at KLOE-2

Aleksander Gajos

doi:10.1051/epjconf/20148103004

Abstract

Quantum entanglement of K and B mesons allows for a direct experimental test of time-reversal symmetry independent of CP violation. The T symmetry can be probed by exchange of initial and final states in the reversible transitions between flavour and CP-definite states of the mesons which are only connected by the T conjugation. While such a test was successfully performed by the BaBar experiment with neutral B mesons, the KLOE-2 detector can probe T-violation in the neutral kaon system by investigating the process with Ks->pi l nu and Kl->3pi0 decays. Analysis of the latter is facilitated by a novel reconstruction method for the vertex of Kl->3pi0 decay which only involves neutral particles. Details of this new vertex reconstruction technique are presented as well as prospects for conducting the direct T symmetry test at the KLOE-2 experiment.

Highlights

Among possible experimental ways to study the T symmetry violation, it is of special interest to test the symmetry directly, i.e. by comparing amplitudes for a process and its time inverse
The only evidence of T violation in the neutral kaon system was found by the CPLEAR experiment through measurement of the Kabir asymmetry [1]
Quantum entanglement of neutral kaons produced at the φ factory allows to obtain and compare kaon transitions between flavour-definite and CP-definite states and their time inverses which are only connected by time reversal conjugation [2]

Summary

Introduction

Among possible experimental ways to study the T symmetry violation, it is of special interest to test the symmetry directly, i.e. by comparing amplitudes for a process and its time inverse. For spin 0 particles such as neutral mesons the inverse process is obtained by the exchange of initial and final states. Quantum entanglement of neutral kaons produced at the φ factory allows to obtain and compare kaon transitions between flavour-definite and CP-definite states and their time inverses which are only connected by time reversal conjugation [2]. This allows for a direct test of the T symmetry independent of CP and CPT. A similar idea was recently used by the BaBar experiment to directly observe T violation in the neutral B meson system [3, 4]. KLOE-2 is capable of performing the first direct T symmetry test with neutral kaons

Principle of the test

Reconstruction of events for the test at KLOE