Calculation of the pion's quark distribution amplitude in lattice QCD with dynamical fermions

We present a calculation of the pion decay constant and of the second moment of the quark distribution amplitude of the pion within full lattice QCD. Measurements are made on ${12}^3$×24 and ${16}^3$×32 lattices, using two flavors of Wilson fermion. Different methods used to extract $f_{\pi }$ give consistent results. We find a better signal for the second moment of the distribution amplitude than in previous lattice calculations and obtain results that are significantly smaller than those obtained from sum-rule calculations and previously in (quenched) lattice QCD.