NUCLEON AXIAL FORM-FACTOR FROM LATTICE QCD

Results for the isovector axial form factors of the proton from a latt ice QCD calculation are presented for both the point-split and local c urrents. They are obtained on a quenched 16(3) x 24 lattice at beta = 6.0 with Wilson fermions for a range of quark masses from strange to t wice the charm mass. For each quark mass, we find that the axial form factor falls off slower than the corresponding proton electric form fa ctor. Results extrapolated to the chiral limit show that the q2 depend ence of the axial form factor agrees quite well with experiment. The a xial vector coupling constant g(A) calculated for the point-split and local currents is 1.20 +/- 0.11 and 1.18 +/- 0.11. The central values are 4% and 6% smaller than the experimental value of 1.254, respective ly. We also consider the large ma correction and renormalization for t he axial vector current of heavy quarks.