Search for CP Violation in the Decay Z -> b (b bar) g

TL;DR

This study analyzed three million Z boson decays to search for CP violation beyond the Standard Model in Z -> b b̄ g decays, finding no evidence and setting limits on anomalous couplings.

Contribution

First search for CP violation in Z -> b b̄ g decays using angular correlations and differential rates with a large data set, establishing new limits on anomalous couplings.

Findings

No CP violation signal detected.

Limits set: .59 on h_b and 3.02 on h_b^* at 95% CL.

Analysis of angular correlations in three-jet events.

Abstract

About three million hadronic decays of the Z collected by ALEPH in the years 1991-1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> b \bar{b} g. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, ${\hat{h}}_b = {\hat{h}}_{Ab}g_{Vb}-{\hat{h}}_{Vb}g_{Ab}$ and $h^{\ast}_b = \sqrt{\hat{h}_{Vb}^{2}+\hat{h}_{Ab}^{2}}$, limits of \hat{h}_b < 0.59$ and $h^{\ast}_{b} < 3.02$ are given at 95\% CL.