Precise determination of V_ud and V_us

TL;DR

This paper reviews recent progress in precisely determining the CKM matrix elements V_ud and V_us, crucial for testing the unitarity of the CKM matrix and the Standard Model's consistency.

Contribution

It provides an organized summary of recent contributions and advancements in the precise measurement of V_ud and V_us from WG1 sessions, highlighting improvements over previous estimates.

Findings

Updated limits on CKM unitarity deviation .0001(6)

Significant recent work improving V_ud and V_us measurements

Progress towards more stringent tests of the Standard Model

Abstract

The actual limit of the unitarity condition of the first row of the CKM matrix |V_ud|^2+|V_us|^2+|V_ub|^2=1+\Delta_CKM is \Delta_CKM=-0.0001(6). In 2010 the same was \Delta_CKM=+0.0001(6). Despite the only difference of a sign, and with an absolute change of the value of one third of the accuracy, a substantial amount of work has been done in the last two years to improve the knowledge of all the contributions to this stringent limit to CKM unitarity, and more is expected in the next years. In this paper we present an organized summary of all the important contributions presented during the WG1 sessions, referring as much as possible to the contribution papers prepared by the individual authors.