Quantum chromodynamics (QCD) is the component of the Standard Model of elementary particle physics that governs the strong interactions. It describes how quarks and gluons, the fundamental entities of strongly interacting matter, are bound together to form strongly interacting particles, such as protons and neutrons, and it determines how these particles in turn interact to form atomic nuclei.

The Standard Model has been enormously successful; however, our knowledge of it is incomplete because it has proven extremely difficult to extract many of the most important predictions of QCD, those that depend on the strong coupling regime of the theory. To do so from first principles and with controlled systematic errors requires large scale numerical simulations within the framework of lattice gauge theory. Such simulations are needed to address problems that are at the heart of the Department of Energy's large experimental programs in high energy and nuclear physics.

Our immediate objectives are to 1) calculate the effects of the strong interactions on weak interaction processes to the accuracy needed to make precise tests of the Standard Model; 2) determine the properties of strongly interacting matter under extreme conditions such as those that existed in the very early development of the universe, and are created today in relativistic heavy ion collisions; and 3) calculate the masses of strongly interacting particles and obtain a quantitative understanding of their internal structure.

In the era of the Large Hadron Collider, starting in 2008, new challenges may await us in new strongly interacting theories beyond the Standard Model, such as dynamically broken supersymmetry, techicolor, or top-color.

SciDAC Review, Fall, 2006: Results from Lattice Quantum Chromodynamics.

Recent physics results

• "The Nucleon axial charge in full lattice QCD", LHPC Collaboration (R.G. Edwards et al.). Phys. Rev. Lett. 96: 052001, 2006, hep-lat/0510062.
• "The Kaon B-parameter from quenched domain-wall QCD". Y. Aoki et al., Phys. Rev. D73:094507, 2006, hep-lat/0508011.
• "The B meson decay constant from unquenched lattice QCD". HPQCD Collaboration (Alan Gray et al.). Phys. Rev. Lett. 95:212001, 2005, hep-lat/0507015
• "The Upsilon spectrum and m(b) from full lattice QCD". HPQCD Collaboration (A. Gray et al.). Phys. Rev. D72:094507, 2005, hep-lat/0507013.
• "Charmed meson decay constants in three-flavor lattice QCD", C. Aubin et al., Phys. Rev. Lett. 95: 122002, 2005, hep-lat/0506030.
• "Accurate determinations of alpha(s) from realistic lattice QCD". HPQCD and UKQCD Collaborations (Q. Mason et al.). Phys. Rev. Lett. 95:052002, 2005, hep-lat/0503005.
• "Mass of the B(c) meson in three-flavor lattice QCD", Ian F. Allison et al. (HPQCD, Fermilab, and UKQCD lattice collaborations), Phys. Rev. Lett. 94:172001, 2005., hep-lat/0411027.
• "The N to Delta electromagnetic transition form-factors from lattice QCD". C. Alexandrou et al., Phys. Rev. Lett. 94:021601, 2005, hep-lat/0409122.
• "Semileptonic decays of D mesons in three-flavor lattice QCD". Fermilab, MILC and HPQCD lattice collaborations (C. Aubin et al.). Phys. Rev. Lett. 94:011601, 2005, hep-ph/0408306.
• "Light pseudoscalar decay constants, quark masses, and low energy constants from three-flavor lattice QCD". MILC Collaboration (C. Aubin et al.). Phys. Rev. D70:114501, 2004 hep-lat/0407028.
• "First determination of the strange and light quark masses from full lattice QCD". HPQCD, MILC, and UKQCD Collaborations (C. Aubin et al.). Phys. Rev. D70:031504, 2004, hep-lat/0405022.
• "QCD thermodynamics with three flavors of improved staggered quarks". MILC Collaboration (C. Bernard et al.). Phys. Rev. D71:034504, 2005, hep-lat/0405029.
• "Transverse structure of nucleon parton distributions from lattice QCD". LHPC and SESAM Collaborations. Phys. Rev. Lett. 93:112001, 2004, hep-lat/0312014.
• "The B(s) and D(s) decay constants in three flavor lattice QCD". HPQCD collaboration, (Matthew Wingate et al.), Phys. Rev. Lett. 92:162001, 2004, hep-ph/0311130.
• "B(K) from quenched QCD with exact chiral symmetry". N. Garron et al., Phys. Rev. Lett. 92:042001, 2004, hep-ph/0306295.
• "High precision lattice QCD confronts experiment". HPQCD, UKQCD, MILC Collaboration and Fermilab Lattice Collaborations (C.T.H. Davies et al.). Phys. Rev. Lett. 92:022001, 2004, hep-lat/0304004.