Enhanced charm CP asymmetries from final state interactions

Abstract

We show that final state interactions (FSI) within a CPT invariant two-channel framework can enhance the charge-parity (CP) violation difference between $D^0\to {\pi }^{-}{\pi }^{+}$ and $D^0\to K^{-}{K}^{+}$ decays up to the current experimental value. This result relies upon: (i) the dominant tree level diagram, (ii) the well-known experimental values for the $D^0\to {\pi }^{-}{\pi }^{+}$ and $D^0\to K^{-}{K}^{+}$ branching ratios, and (iii) the $\pi \pi \to \pi \pi$ and $\pi \pi \to KK$ scattering data to extract the strong phase difference and inelasticity. Based on well-grounded theoretical properties, we find the sign and bulk value of the $\Delta A_{CP}$ and $A_{CP}(D^0\to {\pi }^{-}{\pi }^{+})$ recently observed by the LHCb Collaboration.

Comments: revised version, approved to PRL