Standard Model Prediction for Direct CP Violation in K -> pi pi Decay

摘要

We report the first lattice QCD calculation of the complex kaon decay amplitude A(0) with physical kinematics, using a 323 x 64 lattice volume and a single lattice spacing a, with 1/a = 1.3784(68) GeV. We find Red(A(0)) = 4.66(1.00)(1.26) x 10(-7) GeV and Imd(A(0)) = -1.90(1.23)(1.08) x 10(-11) GeV, where the first error is statistical and the second systematic. The first value is in approximate agreement with the experimental result: Re(A(0)) = 3.3201(18) x 10(-7) GeV, while the second can be used to compute the direct CP-violating ratio Re(epsilon'/epsilon) = 1.38(5.15)(4.59) x 10(-4), which is 2.1 sigma below the experimental value 16.6(2.3) x 10(-4). The real part of A(0) is CP conserving and serves as a test of our method while the result for Re(epsilon'/epsilon) provides a new test of the standard model theory of CP violation, one which can be made more accurate with increasing computer capability.