## Abstract

A long-standing puzzle in charm physics is the large difference between the D ^{0}→ K ^{+}K ^{-} and D ^{0}→ π ^{+}π ^{-} decay rates. Recently, the LHCb and CDF collaborations reported a surprisingly large difference between the direct CP asymmetries, ΔACP, in these two modes. We show that the two puzzles are naturally related in the Standard Model via s- and d-quark "penguin contractions". Their sum gives rise to ΔACP, while their difference contributes to the two branching ratios with opposite sign. Assuming nominal SU(3) breaking, we perform a U-spin based fit to the D ^{0} → K ^{+}π ^{-}; π ^{+}K ^{-} ; π ^{+}π ^{-} ;K ^{+}K ^{-} decay rates, which yields large penguin contractions that naturally explain ΔACP. Expectations for the individual CP asymmetries are also discussed.

Original language | English |
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Article number | 161 |

Journal | Journal of High Energy Physics |

Volume | 2012 |

Issue number | 10 |

DOIs | |

State | Published - 2012 |

Externally published | Yes |

### Funding

Funders | Funder number |
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Directorate for Mathematical and Physical Sciences | 0757868 |

## Keywords

- CP violation
- Standard model

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