### Abstract

We discuss preliminary results for the vector form factors f_{+}^{{π,K}} at zero-momentum transfer for the decays D → π`ν and D → K`ν using MILC’s N_{f} = 2 + 1 + 1 HISQ ensembles at four lattice spacings, a ≈ 0.042,0.06,0.09, and 0.12 fm, and various HISQ quark masses down to the (degenerate) physical light quark mass. We use the kinematic constraint f_{+}(q^{2}) = f_{0}(q^{2}) at q^{2} = 0 to determine the vector form factor from our study of the scalar current, which yields f_{0}(0). Results are extrapolated to the continuum physical point in the framework of hard pion/kaon SU(3) heavy-meson-staggered χPT and Symanzik effective theory. Our calculation improves upon the precision achieved in existing lattice-QCD calculations of the vector form factors at q^{2} = 0. We show the values of the CKM matrix elements |V_{cs}| and |V_{cd}| that we would obtain using our preliminary results for the form factors together with recent experimental results, and discuss the implications of these values for the second row CKM unitarity.

Original language | English (US) |
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Article number | 269 |

Journal | Proceedings of Science |

Volume | 334 |

Publication status | Published - Jan 1 2018 |

Event | 36th Annual International Symposium on Lattice Field Theory, LATTICE 2018 - East Lansing, United States Duration: Jul 22 2018 → Jul 28 2018 |

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### ASJC Scopus subject areas

- General

### Cite this

^{2}= 0.

*Proceedings of Science*,

*334*, [269].