Measurement of the branching ratio of the decay KL -> pi e nu and extraction of the CKM parameter |Vus|

TL;DR

This paper reports a precise measurement of the decay branching ratio of KL -> pi e nu and uses it to extract the CKM matrix element |Vus|, providing important tests of the Standard Model.

Contribution

The study provides a new, more accurate measurement of the KL -> pi e nu decay branching ratio and derives |Vus|, improving constraints on the CKM matrix.

Findings

Measured R = 0.4978 ± 0.0035 for KL -> pi e nu decay.

Derived |Vus|f+(0) = 0.2146 ± 0.0016 from the measurement.

Enhanced precision in CKM matrix element |Vus| estimation.

Abstract

We present a new measurement of the branching ratio R of the decay KL -> pi e nu (Ke3), relative to all charged KL decays with two tracks, based on data taken with the NA48 detector at the CERN SPS. We measure R = 0.4978 +- 0.0035. From this we derive the Ke3 branching fraction and the weak coupling parameter |Vus| in the CKM matrix. We obtain |Vus|f+(0) = 0.2146 +- 0.0016, where f+(0) is the vector form factor in the Ke3 decay.