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I study Quantum Chromodynamics(QCD), the fundamental theory of the strong force. This force binds quarks and gluons together to form protons and neutrons, the fundamental building blocks of matter that make up our world. In principle, QCD describes all of nuclear physics, in the sense that Quantum Electrodynamics describes condensed matter physics. It is also important to particle physics because most of the particles detected in high-energy collider experiments like those at Fermilab's Tevatron and the soon to be complete Large Hadron Collider at CERN are hadrons, the bound states of quarks and gluons.
QCD is a relativistic quantum field theory which describes the interactions of the gluons and quarks. Because the strength of the QCD interaction is intrinsically large, QCD is extremely difficult to solve. Practical calculations, e.g. to predict the mass of the proton, are done through large scale numerical simulations of the QCD vacuum-- a technique known as lattice QCD since space-time is discretized on a four dimensional lattice to make the calculations sensible. These calculations are performed on the world's biggest supercomputers. At Brookhaven National Laboratory (BNL) (where I do much of my research) we are fortunate to have our own special-purpose supercomputer, the QCDSP ("QCD on a digital signal processor"), a massively parallel machine made from 10,000 DSP's, built by my colleagues at Columbia University. Soon the next generation machine being built by Columbia University physicists and IBM, the QCDOC ("QCD on a chip") supercomputer, will arrive at BNL. The QCDOC will perform our simulations at a rate of 5 Tera-FLOPS, or 5 trillion floating-point operations per second.
A topic that we will study with this computer is the structure of the proton. For example, we still do not understand precisely how much of its spin the proton gets from the quarks and how much from the gluons, though we know their contributions must add to 1/2.
At Brookhaven's Relativistic Heavy Ion Collider (RHIC), experimentalists are striving to discover the quark-gluon plasma, a state of matter that existed micro-seconds after the big-bang when the universe was extremely hot. The quark-gluon plasma, or high termperature phase of ordinary matter, was predicted through lattice QCD simulations. This phase transition is a very active research topic.
By simulating QCD, we not only learn about the fundamental nature of matter, but we can also provide crucial tests of the Standard Model of particle physics-- the most fundamental theory of how our universe works. My current research deals with processes that violate a fundamental symmetry between matter and anti-matter (CP symmetry) and also the purely quantum mechanical interactions of muons (heavy electrons) with the QCD vacuum (known as the anomalous magnetic moment, g-2). Such studies may lead to the discovery of new physics, beyond the Standard Model.