The Valence-Quark Distribution of the Kaon from Lattice QCD.

We present the first lattice-QCD calculation of the kaon valence-quark distribution functions using the large-momentum effective field theory (LaMET) approach, a method that has been applied to a wide variety of isovector nucleon distributions and valence pion distributions. This is the first such lattice calculation with multiple pion masses with the lightest one around 220~MeV, 2 lattice spacings $a=0.06$ and 0.12~fm, $(M_\pi)_\text{min} L \approx 5.5$, and high statistics ranging from 11,600 to 61,312 measurements. We also find the valence-quark distribution of pion to be consistent with the FNAL E615 experimental results. Our ratio of the $u$ quark PDF in the kaon to that in the pion agrees with the CERN NA3 experiment. We make predictions of the strange quark distribution of the kaon.