Search for CP Violation in the Decay tau- -> pi- K^0_S (>= 0 pi0) nu_tau

TL;DR

This paper searches for CP violation in tau decay to pi and K0_S particles, using a large dataset, and finds a decay-rate asymmetry slightly deviating from the Standard Model prediction.

Contribution

First search for CP violation in tau- -> pi- K0_S (>= 0 pi0) nu_tau decay with a large dataset, providing new experimental constraints.

Findings

Measured decay-rate asymmetry: -0.45% with uncertainties

Result is approximately three standard deviations from Standard Model

Provides the most precise measurement to date in this decay channel

Abstract

We report a search for CP violation in the decay \tau- -> \pi - \K^0_S (>= 0 \pi 0) \nu_\tau\ using a dataset of 437 million \tau\ lepton pairs, corresponding to an integrated luminosity of 476 fb^{-1}, collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.45 +/- 0.24 +/- 0.11)%, approximately three standard deviations from the Standard Model prediction of (0.33 +/- 0.01)%.