CP violation in $D^0 \to (K^- K^+, \pi^- \pi^+)$ from diquarks

TL;DR

This paper investigates how a color-sextet scalar diquark could explain large CP asymmetries in D0 meson decays, proposing it as a new physics candidate that aligns with experimental data.

Contribution

It introduces the scalar diquark as a novel explanation for CP violation in D0 decays, with specific mass and coupling constraints derived from data.

Findings

Diquark can generate percent-level CP asymmetries.

Constraints on diquark mass and couplings from decay data.

Potential signals in dijet final states at colliders.

Abstract

The explanation of the large CP asymmetries in $D^0\to (\pi^+\pi^-, K^+K^-)$ decays observed by the LHCb collaboration is likely to call for new physics beyond the CKM paradigm. We explore new contributions caused by the color-sextet scalar diquark, and demonstrate that the diquark with the mass of order 1 TeV and nominal couplings with quarks can generate the CP asymmetries at the percent level. Using the experimental data on branching ratios and CP asymmetries of $D^0\to (\pi^+\pi^-, K^+K^-)$, we derive the constraints on the diquark mass and couplings, which can be further examined on hadron colliders in the dijet final states.