Flavor and CP Violation from a QCD-like Hidden Sector

TL;DR

This paper investigates a QCD-like hidden sector at the GeV scale connected to the Standard Model via a TeV mediator, exploring flavor and CP violation effects, and assessing experimental constraints and signals.

Contribution

It provides a detailed analysis of flavor and CP violation in a QCD-like hidden sector, including constraints from current experiments and proposals for future measurements.

Findings

Electric dipole moments do not strongly constrain the scenario.

Constraints depend on the number of dark quark flavors.

Upcoming experiments like Belle-II and KOTO can probe the model.

Abstract

Confining hidden sectors at the GeV scale are well motivated by asymmetric dark matter and naturalness considerations and can also give interesting collider signatures. Here we study such sectors connected to the Standard Model by a TeV scale mediator charged under both QCD and the dark force. Such a mediator admits a Yukawa coupling between quarks and dark quarks which is generically flavour and $CP$ violating. We show that in contrast to expectation, electric dipole moments do not place a strong constraint on this scenario even with $O(1)$ $CP$-violating phases. We also quantitatively explore constraints from $\Delta F=1,2$ processes as a function of the number of dark quark flavours. Finally, we describe the reach of upcoming measurements at Belle-II and KOTO, and we propose new $CP$-odd observables in rare meson decays that may be sensitive to the $CP$-violating nature of the dark sector.