Improved Vcs determination using precise lattice QCD form factors for D → Kℓν

We provide a 0.8%-accurate determination of \ud V\ud c\ud s\ud from combining experimental results for the differential rate of \ud D\ud →\ud K\ud semileptonic decays with precise form factors that we determine from lattice QCD. This is the first time that \ud V\ud c\ud s\ud has been determined with an accuracy that allows its difference from 1 to be seen. Our lattice QCD calculation uses the Highly Improved Staggered Quark (HISQ) action for all valence quarks on gluon field configurations generated by the MILC collaboration that include the effect of \ud u\ud , \ud d\ud , \ud s\ud and \ud c\ud HISQ quarks in the sea. We use eight gluon field ensembles with five values of the lattice spacin…