Particles at the Stanford Linear Accelerator Center (SLAC) should be feeling violated--CP violated, to be precise. By creating millions and millions of the relatively rare B meson, physicists at SLAC have shown that the B mesons do, indeed, violate an important type of symmetry in the subatomic world. In turn, this allows scientists to understand the subtle differences between matter--the stuff that makes up most of the universe--and antimatter, its opposite (but not equal) twin.

CP violation deals with how matter and antimatter have slightly different properties, even when the universe is reflected in a mirror to compensate for some of the disparity. This difference between particles and antiparticles has been observed in K mesons--and the 1980 Nobel Prize for Physics was the result.

Now SLAC physicists have announced that they have spotted the same phenomenon in heavier and rarer B mesons. According to Stewart Smith, the physicist spokesperson for the SLAC project, 650 "golden events" show that the CP violation matches predictions by the standard model, contrary to much weaker initial results released earlier this year (Science, 23 February 2001, p. 1471).

"The hints of dramatic new physics out there are dashed," Smith says. Instead, the findings support the standard model's predictions for the differences between matter and antimatter.

--CHARLES SEIFE

Related sites

The Stanford Linear Accelerator Center