We report the first calculation using physical light-quark masses of the electromagnetic form factor V(z) describing the long-distance contributions to the K+→π+ℓ+ℓ− decay amplitude. The calculation is performed on a 2+1 flavor domain wall fermion ensemble with inverse lattice spacing a−1=1.730(4)GeV. We implement a Glashow-Iliopoulos-Maiani cancellation by extrapolating to the physical charm-quark mass from three below-charm masses. We obtain V(z=0.013(2))=−0.87(4.44), achieving a bound for the value. The large statistical error arises from stochastically estimated quark loops.
@article{arxiv.2202.08795,
title = {Simulating rare kaon decays $K^{+}\to\pi^{+}\ell^{+}\ell^{-}$ using domain wall lattice QCD with physical light quark masses},
author = {P. A. Boyle and F. Erben and J. M. Flynn and V. Gülpers and R. C. Hill and R. Hodgson and A. Jüttner and F. Ó hÓgáin and A. Portelli and C. T. Sachrajda},
journal= {arXiv preprint arXiv:2202.08795},
year = {2023}
}