  Proton decay is one of possible signatures of baryon number violation, which
has to exist to explain the baryon asymmetry and the existence of nuclear
matter. Proton decays must be mediated through effective low-energy baryon
number violating operators made of three quarks and a lepton. We calculate
matrix elements of these operators between the proton and various meson final
states using the direct method. We report on preliminary results of matrix
element calculation done with the 2+1 dynamical flavor domain wall fermions at
the physical point for the first time.
