Semileptonic kaon decays and the precise determination of $V_{us}$

TL;DR

This paper reviews the theoretical inputs for accurately determining the CKM matrix element V_{us} from semileptonic kaon decays, emphasizing electromagnetic corrections, and presents recent efforts to refine these corrections to address the Cabibbo angle anomaly.

Contribution

It introduces a new precise calculation of electromagnetic corrections in kaon decays, enhancing the accuracy of V_{us} measurements and exploring implications for potential new physics.

Findings

Electromagnetic corrections refined to sub-permille accuracy

Improved determination of V_{us} from kaon decays

Insights into the Cabibbo angle anomaly

Abstract

I will give a brief overview of the Standard Model theory inputs needed for the precise determination of the Cabibbo-Kobayashi-Maskawa matrix element $V_{us}$ from semileptonic kaon decays, focusing on the long-distance electromagnetic corrections. I will then describe our recent effort to pin down this correction at sub-permille level, which further sharpens the so-called ``Cabibbo angle anomaly'', an interesting observation which may point towards new physics.