Beyond the Standard Model with Precision Nucleon Matrix Elements on the Lattice

Precision measurements of nucleons provide constraints on the Standard Model and can discern the signatures predicted for particles beyond the Standard Model (BSM). Knowing the Standard Model inputs to nucleon matrix elements will be necessary to constrain the couplings of dark matter candidates such as the neutralino, to relate the neutron electric dipole moment to the CP-violating theta parameter, or to search for new TeV-scale particles though non-$V-A$ interactions in neutron beta decay. However, these matrix elements derive from the properties of quantum chromodynamics (QCD) at low energies, where perturbative treatments fail. Using lattice gauge theory, we can nonperturbatively calculate the QCD path integral on a supercomputer. In this proceeding, I will discuss a few representative areas in which lattice QCD (LQCD) can contribute to the search for BSM physics, emphasizing suppressed operators in neutron decay, and outline prospects for future development.Comment: 3 pages, 2 figures, talk presented at the 19th Particles and Nuclei International Conference (PANIC 2011), Massachusetts Institute of Technology, Cambridge, MA, USA, July 24-29, 201

Charmed spectroscopy from a nonperturbatively determined relativistic heavy quark action in full QCD

We present a preliminary calculation of the charmed meson spectrum using the 2+1 flavor domain wall fermion lattice configurations currently being generated by the RBC and UKQCD collaborations. The calculation is performed using the 3-parameter, relativistic heavy quark action with nonperturbatively determined coefficients. We will also demonstrate a step-scaling procedure for determining these coefficients nonperturbatively using a series of quenched, gauge field ensembles generated for three different lattice spacings.Comment: Proceeding for 24th International Symposium on Lattice Field Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200

Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm)^3. Despite the small volume, the ratio of the isovector vector and axial charges g_A/g_V and that of structure function moments _{u-d}/_{Delta u - Delta d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm)^3. Even with preliminary statistics of 25-30 gauge configurations, the ratios g_A/g_V and _{u-d}/_{Delta u - Delta d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d_1, though yet to be renormalized, appears small in both sets.Comment: 7 pages, 4 figures, talk presented at Lattice 2006, Tucson, Arizona, to be published in PoS(LAT2006)118; replaced Figure 3 with the pion mass squared in GeV^2 unit and corrected a minor error in the abstract in number of gauge configuration