Light quark masses in Nf=2+1 lattice QCD with Wilson fermions

We present a lattice QCD determination of light quark masses with three sea-quark flavours (Nf=2+1). Bare quark masses are known from PCAC relations in the framework of CLS lattice computations with a non-perturbatively improved Wilson-Clover action and a tree-level Symanzik improved gauge action. They are fully non-perturbatively improved, including the recently computed Symanzik counter-term bA−bP. The mass renormalisation at hadronic scales and the renormalisation group running over a wide range of scales are known non-perturbatively in the Schrödinger functional scheme. In the present paper we perform detailed extrapolations to the physical point, obtaining (for the four-flavour theory) mu/d(2 GeV)=3.54(12)(9) MeV and ms(2 GeV)=95.7(2.5)(2.4) MeV in the MS¯ scheme. For the mass ratio we have ms/mu/d=27.0(1.0)(0.4). The RGI values in the three-flavour theory are Mu/d=4.70(15)(12) MeV and Ms=127.0(3.1)(3.2) MeV.