Observed Asymmetry in $\bar{p}p \to \pi^+ K^- K^0 / \pi^- K^+ \bar{K}^0$ and Relation to Reciprocity

TL;DR

This paper discusses the observed charge asymmetry in antiproton-proton annihilation into kaon states, examining its interpretation as T-non-invariance and exploring alternative explanations involving TCP-noninvariance of kaon decays.

Contribution

It analyzes the implications of charge asymmetry observations for fundamental symmetry invariances, contrasting T-invariance and TCP-invariance interpretations.

Findings

Observed asymmetry matches theoretical expectations for T-non-invariance.

Alternative TCP-invariance explanation predicts a larger asymmetry in K_S^0 decays.

The results challenge the straightforward interpretation of asymmetry as T-violation.

Abstract

The charge-asymmetry observed in a recent CPLEAR experiment was interpreted by the authors as a direct observation of T-noninvariance. While this is the simplest and most natural inference, and the observed effect agrees in sign and magnitude with theoretical expectation, adherents of T-invariance may argue that other interpretations are also possible. If K^0 and \bar{K}^0 are produced equally in \bar{p} p annihilation, and T-invariance is assumed to hold, the asymmetry observed in CPLEAR must be attributed to TCP-noninvariance of kaon beta-decays. If that were the case, the charge-asymmetry in K_S^0 \to \pi l\nu decays should be three times larger than the one observed for K_L^0 decays.