Cabibbo anomaly versus electroweak precision tests: An exploration of extensions of the Standard Model

TL;DR

This paper investigates the Cabibbo anomaly within the Standard Model Effective Field Theory, revealing a discrepancy with electroweak precision observables and analyzing potential Standard Model extensions and future experimental impacts.

Contribution

It demonstrates a mismatch between the Cabibbo anomaly and electroweak data and assesses possible Standard Model extensions and future collider measurements.

Findings

Discrepancy between $R(V_{us})$ and EWPO in a single operator scenario

Standard Model extensions cannot fully reconcile current data

Future colliders like ILC or FCC-ee could influence the tension

Abstract

There is a newly emerging tension between determinations of $V_{us}$ from different sources (known as the Cabibbo anomaly), which is clearly demonstrated by the new $R(V_{us})$ observable. We explore this observable from the perspective of the Standard Model Effective Field Theory and show there is a discrepancy between $R(V_{us})$ and existing electroweak precision observables (EWPO) in a simple single operator dominated scenario. We explore all possible single particle extensions of the Standard Model that can generate the Cabibbo anomaly effect and show how they cannot reconcile the current data. We further examine the future of EWPO at the ILC or FCC-ee experiments and discuss the effect on the tension of a change in specific EW observables.