Continuum Limit of Overlap Valence Quarks on a Twisted Mass Sea
K. Cichy1 , G. Herdoiza2,3 , K. Jansen2
1 Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, PL 61-614 Poznań, Poland
2 NIC, DESY, Platanenallee 6, D-15738 Zeuthen, Germany
3 Departamento de Física Teórica and Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain
Nuclear Physics, B847, 179-196 (2011)
We study a lattice QCD mixed action with overlap valence quarks on two flavours of Wilson maximally twisted mass sea quarks. Employing three different matching conditions to relate both actions to each other, we investigate the continuum limit by using three values of the lattice spacing ranging from 0.05 fm to 0.08 fm. A particular emphasis is put on the effect on physical observables of the topological zero modes appearing in the valence overlap operator. We estimate the region of parameter space where the contribution from these zero modes is sufficiently small such that their effects can be safely controlled and a restoration of unitarity of the mixed action in the continuum limit is reached.