$D$-meson semileptonic form factors at zero momentum transfer in (2+1+1)-flavor lattice QCD

Abstract

We present a calculation of the $D\to K\ell \nu$ and $D\to \pi \ell \nu$ semileptonic form factors at $q^2=0$, which enable determinations of the CKM matrix elements $|V_{cs}|$ and $|V_{cd}|$, respectively. We use gauge-field configurations generated by the MILC collaboration with four flavors of highly-improved staggered (HISQ) quarks, analyzing several ensembles including those with physical pion masses and approximate lattice spacings ranging from 0.12~fm to 0.042~fm. We also use the HISQ action for the valence quarks. We employ twisted boundary conditions to calculate the form factors at zero momentum transfer directly. We use heavy-light-meson chiral perturbation theory modified for energetic pions and kaons, and supplemented by terms to describe the lattice-spacing dependence, to obtain preliminary results at the physical point and in the continuum limit.

Comments: 7 pages, 6 figure, Lattice 2015