title: Up quark mass in lattice QCD with three light dynamical quarks and implications for strong CP invariance.
abstract: A standing mystery in the standard model is the unnatural smallness of the strong CP violating phase. A massless up quark has long been proposed as one potential solution. A lattice calculation of the constants of the chiral Lagrangian essential for the determination of the up quark mass, 2alpha(8)-alpha(5), is presented. We find 2alpha(8)-alpha(5)=0.29+/-0.18, which corresponds to m(u)/m(d)=0.410+/-0.036. This is the first such calculation using a physical number of dynamical light quarks, N(f)=3.
authors.affiliation: Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Nelson
authors.forename: George T
authors.initials: GT
authors.lastname: Fleming
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Kilcup