SciDAC LQCD: Hadron Structure at Light Quark Masses

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2007 Proposals

Abstract

A comprehensive research program is proposed for the first full QCD calculations of hadron structure extending to the chiral regime of light quark masses, using a hybrid combination of chiral domain wall valence quarks and dynamical improved staggered sea quark configurations provided by the MILC collaboration. Physical observables will include moments of structure functions, form factors, generalized form factors, the nucleon sigma term, the neutron electric dipole moment, nucleon density-density correlation functions, nucleon electric and magnetic polarizability, hadron wave functions, the nucleon to Delta transition form factors, the pion form factor, pentaquark observables, and related spectroscopic quantities. Operator renormalization will be calculated perturbatively in all cases and checked non-perturbatively in selected cases. Calculations are proposed at three lattices spacings: a = 0.13 fm using lattices with ml ms = 0.6, 0.4, 0.2, 0.14, and 0.1; a = 0.09 fm with ml ms = 1, 0.4, 0.2, and 0.1; and a = 0.4 fm at ml m = 0.4.

See the current proposal (pdf)

Abstract

We propose to use USQCD resources at BNL, JLab or FNAL for the generation of lattice configurations using 2+1 flavors of domain wall dynamical fermions. This work would provide two new streams of configurations with size 32^3 64, lattice spacing a = 0.093 fm and light quark masses of 1/5 and 1/7 of the strange quark mass. We also describe further generation of lattice configurations with smaller quark masses and appropriately larger volumes which would provide an important extension to this work and could be carried out on additional resources expected to become available at other DOE facilities. In addition to this configuration generation, we also propose to use a modest fraction (20%) of this time to calculate series of "standard" fermion propagators measured with a smeared Gaussian source and quark masses which match those used in generating the configurations. Our complete proposal requests 60 million QCDOC processor hours (eight of the twelve QCDOC racks at BNL) or the equivalent spread across the various available resources.

See the current proposal (pdf)