1212.3188 (Peter A. Boyle et al.)

Kaon semileptonic decays near the physical point    [PDF]

Peter A. Boyle, Jonathan M. Flynn, Andreas Jüttner, Christopher Sachrajda, Karthee Sivalingam, James M. Zanotti

The CKM matrix element $|V_{us}|$ can be extracted from the experimental measurement of semileptonic $K\to\pi$ decays. The determination depends on theory input for the corresponding vector form factor in QCD. We present a preliminary update on our efforts to compute it in $N_f=2+1$ lattice QCD using domain wall fermions for several lattice spacings and with a lightest pion mass of about $170\,\mathrm{MeV}$. By using partially twisted boundary conditions we avoid systematic errors associated with an interpolation of the form factor in momentum-transfer, while simulated pion masses near the physical point reduce the systematic error due to the chiral extrapolation.

View original: http://arxiv.org/abs/1212.3188