Determining the low energy parameters of Wilson Chiral Perturbation Theory

We report preliminary results of a Wilson Chiral Perturbation Theory (WChPT) analysis of twisted mass lattice QCD data. The quenched data, previously published by two different groups, was generated with two definitions for the critical quark mass and shows a strong non-linear quark mass dependence for small quark masses for the pion mass definition (``bending phenomenon''). We find that WChPT describes this characteristic curvature fairly well. Fits to the data provide estimates for combinations of low-energy parameters, even though the errors are sizable.