Chiral perturbation theory with Wilson-type fermions including a2 effects:: Nf=2 degenerate case -: art. no. 054508

We derive the quark mass dependence of m(pi)(2), m(AWI), and f(pi), using chiral perturbation theory, which includes the a(2) effect associated with the explicit chiral symmetry breaking of the Wilson-type fermions, in the case of the N-f=2 degenerate quarks. The distinct features of the results are (1) the additive renormalization for the mass parameter m(q) in the Lagrangian, (2) O(a) corrections to the chiral log (m(q)log m(q)) term, (3) the existence of a more singular term log m(q) generated by a(2) contributions, and (4) the existence of both m(q)log m(q) and log m(q) terms in the quark mass from the axial Ward-Takahashi identity m(AWI). By fitting the mass dependence of m(pi)(2) and m(AWI), obtained by the CP-PACS Collaboration for N-f=2 full QCD simulations, we find that the data are consistently described by the derived formulas. Resumming the most singular terms log m(q), we also derive modified formulas, which show a better control over the next-to-leading order correction.