# Quark Seesaw, Dark $U(1)$ symmetry and Baryon-Dark Matter Coincidence

## TL;DR

This paper presents a model extending the standard model with a dark U(1) symmetry and a quark seesaw mechanism, explaining the baryon-dark matter coincidence through simultaneous asymmetry generation and providing testable predictions for dark matter detection.

## Contribution

It introduces a novel quark seesaw extension with a dark U(1) symmetry and heavy neutral fermions, offering a unified explanation for baryon and dark matter abundances.

## Key findings

- Dark matter mass near proton mass explains abundance coincidence.
- Model predicts testable signals in low-threshold dark matter experiments.
- Symmetric dark matter component is eliminated via annihilation processes.

## Abstract

We attempt to understand the baryon-dark-matter coincidence problem within the quark seesaw extension of the standard model where parity invariance is used to solve the strong CP problem. The $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge symmetry of this model is extended by a dark $U(1)_X$ group plus inclusion of a heavy neutral vector-like fermion $\chi_{L,R}$ charged under the dark group which plays the role of dark matter. All fermions are Dirac type in this model. Decay of heavy scalars charged under $U(1)_X$ leads to simultaneous asymmetry generation of the dark matter and baryons after sphaleron effects are included. The $U(1)_X$ group not only helps to stabilize the dark matter but also helps in the elimination of the symmetric part of the dark matter via $\chi-\bar{\chi}$ annihilation. For dark matter mass near the proton mass, it explains why the baryon and dark matter abundances are of similar magnitude (the baryon-dark-matter coincidence problem). This model is testable in low threshold (sub-keV) direct dark matter search experiments.