College Park, MD -
August 3, 2004 - Drs.
Jawahery and Doug
Roberts, professors in the University of Maryland Department
of Physics, and their colleagues working on the BaBar experiment,
have discovered a drastic difference in the behavior of matter and
antimatter. In fact, they have discovered the first statistically
significant evidence of direct charge parity (CP) violation in B
"B meson" refers
to heavy particles containing the bottom quark (b). B mesons and
anti-B mesons are formed by colliding electrons and their antimatter
counterparts, positrons, and then decay in a short time period.
CP violation is what occurs when the matter and antimatter decays
are counted and the numbers are unequal. In other words, the decay
rates are different.
The BaBar scientists
used the PEP-II accelerator at the Stanford
Linear Accelerator Center (SLAC), a Department of Energy laboratory
operated by Stanford University, to collide the electrons and positrons
and form millions of B mesons and anti-B mesons. The study of more
than 200 million pairs of these particles showed that the anti-B
mesons decayed significantly faster.
BaBar, as well as other
experiments in the field of particle physics, has observed matter-antimatter
asymmetries before. However, this is the first time that direct
charge parity (CP) violation has been observed in B decays and used
to explain the asymmetric behavior. This result is one integral
step to better understanding the matter and antimatter and, in turn,
the nature of the world we live in.
may bring us one step closer to understanding why the universe today
consists only of matter when, after the Big Bang, matter and antimatter
were both present - and in approximately equal amounts," says
While BaBar is a collaboration
of approximately 600 scientists from all over the world, these particular
measurements were the focus of the work of Jawahery and his students
and research associates since the start of the BaBar experiment.
In addition to his current students and research associates, several
of his former students and postdoctoral associates are now collaborators
from other institutions. For example, Maryland alum Dr. Amir Farbin
wrote his thesis on the topic and is now at the University of Chicago.
Dr. James Olson, who was a postdoctoral associate under Professor
Jawahery, is now an assistant professor at Princeton University
and one of the leaders of the analysis of the experiment.
For more information,
please visit the following links:
Physical Review Letters journal article:
SLAC Press Release:
University of Maryland Department of Physics
University of Maryland High Energy Physics Group