Strong-Isospin Breaking in the Neutron-Proton Mass Difference

Abstract

We determine the strong-isospin violating component of the neutron-proton mass difference from fully-dynamical lattice QCD and partially-quenched QCD calculations of the nucleon mass, constrained by partially-quenched chiral perturbation theory at one-loop level. The lattice calculations were performed with domain-wall valence quarks on MILC lattices with rooted staggered sea-quarks at a lattice spacing of b ~ 0.125 fm, lattice spatial size of L~2.5 fm and pion masses ranging from m_pi~290 MeV to ~350 MeV. At the physical value of the pion mass, we predict M_n - M_p |(d-u) = 2.26 +- 0.57 +- 0.42 +- 0.10 MeV where the first error is statistical, the second error is due to the uncertainty in the ratio of light-quark masses, eta=m_u/m_d, determined by MILC, and the third error is an estimate of the systematic due to chiral extrapolation.

7 pages, 2 figs. Talk given at 24th International Symposium on Lattice Field Theory: Lattice 2006, Tucson, Arizona, 23-28 July 2006

References in corpus (6)

• Strong-Isospin Violation in the Neutron-Proton Mass Difference from Fully-Dynamical Lattice QCD and PQQCD
• Staggered Chiral Perturbation Theory and the Fourth-Root Trick
• Renormalization-group analysis of the validity of staggered-fermion QCD with the fourth-root recipe
• Lattice fermions with complex mass
• Validity of the Rooted Staggered Determinant in the continuum limit
• Flavor extrapolations and staggered fermions