Lattice study of meson correlators in theϵ-regime of two-flavor QCD

We calculate mesonic two-point functions in the $ϵ$-regime of two-flavor QCD on the lattice with exact chiral symmetry. We use gauge configurations of size 16³×32 at a~0.11 fm generated with dynamical overlap fermions. The sea quark mass is fixed at around 3 MeV and the valence quark mass is varied in the range 1--4 MeV, both of which are in the $ϵ$-regime. We find a good consistency with the expectations from the next-to-leading order calculation in the $ϵ$-expansion of (partially quenched) chiral perturbation theory. From a fit we obtain the pion decay constant F=87.3(5.6) MeV and the chiral condensate ΣMS̄=[239.8(4.0) MeV]³ up to next-to-next-to-leading order contributions.