Combined analysis of the unitarity triangle and CP violation in the Standard Model

TL;DR

This paper combines recent experimental data and lattice QCD results to analyze the unitarity triangle and CP violation, highlighting uncertainties in theoretical predictions of epsilon'/epsilon and suggesting deviations from simplified models.

Contribution

It provides a comprehensive combined analysis of CP violation and the unitarity triangle using latest data and lattice results, emphasizing the role of non-perturbative parameters.

Findings

Lattice results for Q_8 matrix element are used without strange quark mass dependence.

Theoretical epsilon'/epsilon estimates are (4-7) x 10^(-4), with large uncertainties.

Experimental data indicate significant deviation of Q_6 matrix element from vacuum-saturation approximation.

Abstract

We perform a combined analysis of the unitarity triangle and of the CP violating parameter epsilon'/epsilon using the most recent determination of the relevant experimental data and, whenever possible, hadronic matrix elements from lattice QCD. We discuss the role of the main non-perturbative parameters and make a comparison with other recent analyses. We use lattice results for the matrix element of Q_8 obtained without reference to the strange quark mass. Since a reliable lattice determination of the matrix element of Q_6 is still missing, the theoretical predictions for epsilon'/epsilon suffer from large uncertainties. By evaluating this matrix element with the vacuum-saturation approximation, we typically find as central value epsilon'/epsilon = (4 - 7) x 10^(-4). We conclude that the experimental data suggest large deviation of the value of the matrix element of Q_6 from the vacuum-saturation approximation, possibly due to penguin contractions.