CP violation in D0→(K ^-K ⁺,π ^-π ⁺) from diquarks

The explanation of the large CP asymmetries in D0→(π ⁺π ^-,K ⁺K ^-) decays observed by the LHCb collaboration is likely to call for new physics beyond the Cabibbo-Kobayashi-Maskawa quark-mixing matrix (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 D0→(π ⁺π ^-,K ⁺K ^-), we derive the constraints on the diquark mass and couplings, which can be further examined in hadron colliders in the dijet final states.