Electroweak Constraints from Atomic Parity Violation and Neutrino Scattering

TL;DR

This paper explores how atomic parity violation and neutrino scattering experiments can constrain new physics beyond the Standard Model by analyzing oblique corrections characterized by parameters S and T.

Contribution

It provides new constraints on the oblique parameter S from atomic parity violation data and discusses the potential of future neutrino scattering experiments to improve these constraints.

Findings

Atomic parity violation experiments constrain S parameter.

Top quark mass imposes stringent S constraints.

Future neutrino experiments could enhance S and T bounds.

Abstract

Precision electroweak physics can provide fertile ground for uncovering new physics beyond the Standard Model (SM). One area in which new physics can appear is in so-called "oblique corrections", i.e., next-to-leading order expansions of bosonic propagators corresponding to vacuum polarization. One may parametrize their effects in terms of quantities $S$ and $T$ that discriminate between conservation and non-conservation of isospin. This provides a means of comparing the relative contributions of precision electroweak experiments to constraints on new physics. Given the prevalence of strongly $T$-sensitive experiments, there is an acute need for further constraints on $S$, such as provided by atomic parity-violating experiments on heavy atoms. We evaluate constraints on $S$ arising from recently improved calculations in the Cs atom. We show that the top quark mass $m_t$ provides stringent constraints on $S$ within the context of the Standard Model. We also consider the potential contributions of next-generation neutrino scattering experiments to improved $(S,T)$ constraints.