The kaon semileptonic form factor with near physical domain wall quarks

Abstract

We present a new calculation of the K → π semileptonic form factor at zero momentum transfer in domain wall lattice QCD with N f = 2+1 dynamical quark flavours. By using partially twisted boundary conditions we simulate directly at the phenomenologically relevant point of zero momentum transfer. We perform a joint analysis for all available ensembles which include three different lattice spacings (a = 0.09 - 0.14 fm), large physical volumes (m π L > 3.9) and pion masses as low as 171 MeV. The comprehensive set of simulation points allows for a detailed study of systematic effects leading to the prediction f+Kπ(0)=0.9670(20) (-46+18), where the first error is statistical and the second error systematic. The result allows us to extract the CKM-matrix element | Vu|=0.2237(-8+13) and confirm first-row CKM-unitarity in the Standard Model at the sub per mille level. © 2013 SISSA, Trieste, Italy.