Part of Award-Winning Team
Nelson is part of a team called the “NA31 Collaboration,”
a group that performed anti-matter experiments. The award went to
the entire group of researchers—73 in all, including only four Americans—who
worked on experiments that “showed for the first time direct charge-parity
violation in the decays of neutral K mesons,” according to the award
Charge-parity, or CP, violation is thought to be
the reason why the universe is made of matter, even though equal
amounts of matter and anti-matter should have been created in the
This year’s EPS award to the NA31 Collaboration,
which is led by Heinrich Wahl, is the first time an EPS award has
been given to a group.
The European Physical Society prize has been awarded
since 1989. David Gross, director of the Kavli Institute for Theoretical
Physics and winner of the 2004 Nobel Prize in physics, won the EPS
prize in 2003.
Nelson explained that in particle physics, unlike
theoretical physics, the scientists must work in large teams to
carry out experiments. Nelson arrived at CERN in 1987 and helped
build the portion of the apparatus that distinguished among the
various types of particles that travel at speeds approaching the
speed of light.
Nelson is currently working with another group
of physicists in the highly competitive international search for
“dark matter.” His group is called the Cryogenic Dark Matter Search,
or CDMS, and is considered the leading research endeavor on this
issue. He explained that reliable data indicate that most of the
matter in the universe emits no detectable light. The “dark” matter
is inferred, generally, from the gravitational pull that it exerts
on the matter that does emit light.
A simple explanation would be that the dark matter
consists of protons and other atomic nuclei, which for some reason
do not emit light. However, Nelson noted that this explanation is
inconsistent with our understanding of the Big Bang, and that the
dark matter must consist of a new type of “exotic” particle.