Novel and Updated Bounds on Flavor-Violating Z Interactions in the Quark Sector

TL;DR

This paper establishes new bounds on flavor-violating Z boson interactions with quarks, showing that low-energy experiments currently impose more stringent constraints than collider searches.

Contribution

The paper derives updated bounds on flavor-violating Z couplings to quarks and projects future sensitivities, improving upon previous limits.

Findings

Current bounds on FV couplings are around 10^{-9} for certain quark pairs.

Low-energy experiments outperform collider searches in constraining FV couplings.

Future experiments could further tighten these bounds.

Abstract

We derive bounds on the flavor-violating (FV) couplings of the $Z$ boson to quarks and present future sensitivity projections. Our analysis shows that the current bounds on the FV couplings are $\mathcal{O}(10^{-9})$ for the $Z$ couplings to $cu$ and $sd$, $\mathcal{O}(10^{-7})$ for $bd$, $\mathcal{O}(10^{-6})$ for $bs$, and $\mathcal{O}(10^{-3})$ for $tu$ and $tc$. Overall, low-energy flavor experiments provide significantly stronger constraints on these FV couplings than current collider searches.