Impact of colored scalars on $D^0-\bar D^0$ mixing in diquark models

TL;DR

This paper investigates how colored scalar particles in diquark models influence $D^0-ar D^0$ mixing, providing constraints on model parameters and explaining small couplings via flavor mixing suppression.

Contribution

It analyzes the effects of specific diquark states on $D^0-ar D^0$ mixing and derives constraints, highlighting the role of flavor structure in coupling suppression.

Findings

$ riangle m_D$ imposes the strongest constraints on diquark parameters.

Small couplings can be explained by suppressed flavor mixing.

Diquarks with certain quantum numbers contribute at different loop levels.

Abstract

Inspired by the recent observation of the $D^0-\bar D^0$ mixing, we explore the effects of colored scalars on the $\Delta C=2$ process in diquark models. As an illustration, we investigate the diquarks with the quantum numbers of (6, 1, 1/3) and (6, 1, 4/3) under $SU(3)_C\times SU(2)_L\times U(1)_Y$ gauge symmetries, which contribute to the process at one-loop and tree levels, respectively. We show that $\Delta m_D$ gives the strongest constraint on the free parameters. In addition, we find that the small couplings can be naturally interpreted by the suppressed flavor mixings if the diquark of (6, 1, 4/3) only couples to the third generation.