Recent CP violation and |Vus| measurements from the NA48 experiment

TL;DR

The NA48 experiment at CERN has provided new measurements of CP violation parameters and |Vus|, improving constraints on the CKM matrix through decay rate ratios and asymmetry analyses in kaon decays.

Contribution

This paper presents the latest precise measurements of CP violation parameters and |Vus| from NA48, offering new experimental data to test the Standard Model and CKM matrix consistency.

Findings

Measured |eta+-| related to CP violation parameters.

Determined decay rate ratios for kaon decays.

Deduced |Vus| from branching fractions.

Abstract

Results from recent analyses of the NA48 experiment at CERN are compared with other experiments and confronted with theoretical predictions to provide constraints on the CKM matrix and on CP Violation. The observable eta+- is related to the parameters of indirect and direct CPV (eta+- = epsilon + epsilon'). |eta+-| has been determined by measuring the ratio of decay rates: Gamma(K_L to pi+pi-)/Gamma(K_L to pi e nu), using an NA48 run with a dedicated pure high-intensity K_L beam. The main objective of NA48/2 has been to search for direct CP violation by high precision measurement of the asymmetry A_g = (g+ - g-)/(g+ + g-) of the linear slope parameter g in the Dalitz plot of K+- to 3pi decays. The final results from all data samples are summarised and discussed. The decay rates R(Ke3/K2pi), R(Kmu3/K2pi) and R(Kmu3/Ke3) have been measured with charged K decays from special data samples with a low bias trigger in the NA48/2 experiment. Using the latest PDG average for the (K+- to pi+- pi0) normalisation channel, the Ke3 and Kmu3 branching fractions are then used as input to deduce the CKM matrix element Vus.