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

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.

Comments: 11 pages, 3 figures, references added, final version to appear PLB