First Search for CP Violation in Tau Lepton Decay

TL;DR

This paper reports the first experimental search for CP violation in tau lepton decay using the CLEO II detector, testing a phenomenon predicted by theories beyond the Standard Model.

Contribution

It introduces a novel observable asymmetry to detect CP violation in tau decays and provides the first experimental constraints on this effect.

Findings

No evidence of CP violation was observed.

The results set limits on CP violation in tau decays.

The method can be applied to future experiments.

Abstract

Using the CLEO II detector we have performed the first search for $CP$ violation in tau lepton decay. CP violation in lepton decay does not occur in the minimal standard model but can occur in extensions such as the multi-Higgs doublet model. It appears as a characteristic difference between the $\tau^+$ and $\tau^-$ decay angular distributions for the semi-leptonic decay modes such as $\tau^- \to K^0 \pi^- \nu$. We define an observable asymmetry to exploit this and find no evidence for any CP violation.