Nathan Isgur

Physicists have difficulty studying individual quarks, because these smallest particles of matter are always bound together in pairs or groups of three. The heaviest of the six quarks found in nature have been the most baffling. But such studies are easier now, thanks to a method for understanding quarks developed in the early 1990s. "Heavy quark effective theory" enables physicists to deduce the individual behavior of one type of quark (the bottom quark) by showing how its properties can be directly inferred from measurements of another type (the charm quark). The six quarks identified in nature (in order of increasing mass) are distinguished by the terms up, down, strange, charm, bottom, and top. The heaviest (the top quark) is about 100,000 times the mass of the lightest (the up quark). The theory is based on seven years of theoretical work by Nathan Isgur of Thomas Jefferson National Laboratory and Mark Wise of California Institute of Technology, and a third researcher working independently.

Scientific Impact: This theory made it easier to study bottom quarks and pairs of them—important particles in ongoing studies of why the universe favors matter over its mirror image, antimatter. These papers also have generated thousands of other papers that offer new insight into another theory describing the "strong force" that binds subnuclear particles such as quarks.

Social Impact: These studies help answer questions about the constituents and history of the universe, extending human understanding of nature and contributing to improvements in science education. In addition, although basic research is by definition a search for new knowledge without regard to its practical implications, such work often contributes to technologies with commercial value; examples include computers, lasers, and cancer treatments.

Reference: N. Isgur and M.B. Wise, Phys. Lett. B232, 113 (1989); 237, 527 (1990); Heavy Quark Physics, Aneesh V. Manohar, Mark B. Wise, Cambridge University Press (2000).

URL: http://www.jlab.org/div_dept/theory/favorites/spectroscopy.html

Technical Contact: Linda Ware, ware@jlb.org

Press Contact: Jeff Sherwood, DOE Office of Public Affairs, 202-586-5806

SC-Funding Office: Office of High Energy and Nuclear Physics