2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/194615We present the first results for neutral kaon mixing using 2+1 flavors of domain wall fermions. A new approach is used to extrapolate to the physical up and down quark masses from our numerical studies with pion masses in the range 240 -- 420 MeV; only $SU(2)_L \times SU(2)_R$ chiral symmetry is assumed and the kaon is not assumed to be light. Our main result is $B_K^{\bar{\rm MS}}(2 \mathrm{GeV}) = 0.524(10)(28)$ where the first error is statistical and the second incorporates estimates for all systematic errors.4 pages, 4 figures. RBC and UKQCD collaborationsHigh Energy Physics - PhenomenologyHigh Energy Physics - Latticetext