Apparatus used to regenerate short-lived K mesons for the CP experiment.

Early in the evolution of the universe, matter and its mirror image, antimatter, were equally abundant; but today, antimatter is rare, for reasons not fully understood. A recent observation at Fermi National Accelerator Laboratory lessened the mystery somewhat. The 1999 experiment focused on mesons, short-lived pairings of a quark particle and the corresponding anti-quark. The researchers observed direct charge-parity (CP) violation in the decay of K mesons, or kaons, supporting the picture of CP violation provided in the Standard Model, physicists' current theory of matter and the forces of nature. The phenomenon of CP violation—which shows that matter and antimatter do not always behave symmetrically—was first discovered in kaon processes at Brookhaven National Laboratory in 1964, resulting in a 1980 Nobel Prize for Val Fitch and James Cronin. The definitive nature of the Fermilab result was dramatic and unexpected.

Scientific Impact: The result established the existence of direct CP violation beyond reasonable doubt and eliminated the long-standing hypothesis of a proposed "superweak" interaction as its source. This was a significant advance in understanding of the asymmetry in the behavior of matter and antimatter.

Social Impact: CP violation may be responsible for the survival of matter—including humans—and the disappearance of antimatter. Thus, this research extends human understanding of the origin and history of the universe and contributes to improvements in science education.

Reference: Phys. Rev. Lett. 83, 22 (1999). hep-ex/9905060.

URL: http://www.aip.org/physnews/graphics/html/violate.htm
http://kpasa.fnal.gov:8080/public/epsprime/press_release.html
http://kpasa.fnal.gov:8080/public/epsprime/epoe_intro.html

Technical Contact: Prof. Edward Blucher, blucher@uchepa.uchicago.edu

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

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