First-Generation New Physics in Simplified Models: From Low-Energy Parity Violation to the LHC

TL;DR

This paper investigates how new physics affecting first-generation quark-lepton interactions can be constrained by combining LHC data, low-energy parity violation experiments, and electroweak precision tests, using simplified models and effective field theory.

Contribution

It provides a comprehensive analysis of simplified models linking first-generation quark-lepton interactions to various experimental constraints and future prospects.

Findings

Constraints from LHC, parity violation, and electroweak data are complementary.

Parity violation experiments can help distinguish between different NP scenarios.

Projected future experiments will significantly tighten bounds on first-generation NP interactions.

Abstract

New-physics (NP) constraints on first-generation quark-lepton interactions are particularly interesting given the large number of complementary processes and observables that have been measured. Recently, first hints for such NP effects have been observed as an apparent deficit in first-row CKM unitarity, known as the Cabibbo angle anomaly, and the CMS excess in $q\bar q\to e^+e^-$. Since the same NP would inevitably enter in searches for low-energy parity violation, such as atomic parity violation, parity-violating electron scattering, and coherent neutrino-nucleus scattering, as well as electroweak precision observables, a combined analysis is required to assess the viability of potential NP interpretations. In this article we investigate the interplay between LHC searches, the Cabibbo angle anomaly, electroweak precision observables, and low-energy parity violation by studying all simplified models that give rise to tree-level effects related to interactions between first-generation quarks and leptons. Matching these models onto Standard Model effective field theory, we derive master formulae in terms of the respective Wilson coefficients, perform a complete phenomenological analysis of all available constraints, point out how parity violation can in the future be used to disentangle different NP scenarios, and project the constraints achievable with forthcoming experiments.