$N_f=1+2$ mass dependence of the topological susceptibility

Abstract

A massless up quark has long been proposed as a solution to the strong CP problem. While this solution is sometimes thought to have been excluded, it is actually still ill-defined. In this work, we study the mass dependence of the physical observable ${\chi }_t$, the topological susceptibility. Assigning an unphysically large value to the down mass allows to be more sensitive to the non-perturbative effects behind the $m_u=0$ ambiguity. Preliminary results are presented for four masses of clover fermions.

Comments: 6 pages, talk presented at 34th annual International Symposium on Lattice Field Theory, 24-30 July 2016, University of Southampton, UK