Speaker
Qiu Liu
(Columbia University)
Description
We report a direct lattice calculation of the K-->pipi decay matrix elements for both Delta I=1/2 and 3/2 channels on 2+1 flavor, domain wall fermion, 16^3X32 lattices. This first direct calculation of the Delta I=1/2 channel is made possible by collecting very large statistics and studying the decay at pi-pi threshold with 420 MeV pions in a small, 1.8 fm box. All possible contractions are carefully listed and calculated and identities among them are verified. The decay into the isospin zero pi-pi final state, which receives contributions from the disconnected graphs, is very difficult to calculate, but a clear signal in the similar disconnected pi-pi correlator can be seen. We also demonstrate that a large explicit subtraction of the divergent (sbar gamma_5 d) contribution is necessary even for the case of kinematics which are nominally energy conserving.
Preliminary results, some with large errors, will be presented for the various contributions to the renormalized weak matrix elements A_0 and A_2 in the case of M_pi=420MeV. Delta I=1/2 Rule is demonstrated from our calculation.
