Dynamical twisted mass fermions with light quarks

We present results of dynamical simulations of Nf=2 degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses 300MeV≲mPS≲550MeV. Reaching such small masses was made possible owing to a recently developed variant of the HMC algorithm. The simulations are performed at one value of the lattice spacing a≲0.1fm. In order to have O(a) improvement and aiming at small residual O(a2) cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, l¯3 and l¯4 are evaluated with small statistical errors.