By Neil Calder
Antimo Palano from BABAR
presented evidence for the identification of a new subatomic particle
named Ds(2317) in the Auditorium on Monday, April 28. Initial studies
indicate that the particle is an unusual configuration of a ‘charm’ quark and a ‘strange’
"Congratulations to BABAR!"
said Director Jonathan Dorfan. "The discovery of this new particle
underlines the vigor of our high energy physics research program. The
existence of the particle is not a surprise, but its mass is lower than
expected. This result will send theorists back to their drawing boards."
Evidence from BABAR
for the new particle Ds(2317). The large bumps near the center of the
two figures are produced by decays of the new particle into a system
consisting of a Ds(1969) meson and a neutral pi-meson.
(image courtesy of BABAR)
"This is an important achievement for BABAR,"
said Marcello Giorgi (INFN/University of Pisa), spokesman for the
collaboration. "We have discovered a new charm particle in an experiment
designed to probe the difference between matter and antimatter using
bottom quarks. Sometimes the most exciting discoveries come from
unexpected directions. There has been a buzz of excitement in the
experiment in the past few weeks as we performed all possible checks to
verify the reality of this new intriguing particle. By carefully studying
the experimental data taken since 1999 we have been able to publish a
precise measurement of its mass—2317 Mega-electron Volts. SLAC’s
accelerator people have done a fantastic job in providing us with all this
Six types of quarks are present in nature. The up and down
quarks are the lightest, and are found within the nuclei of atoms of
ordinary matter. Heavier quarks were present in the early universe and are
created today in particle accelerators and in collisions of cosmic rays
with atoms in the earth’s atmosphere.
SLAC has a long tradition of discovery in the physics of
charm quarks, beginning with the Nobel Prize-winning discovery of the
first such particle, a charm-anti-charm system, in 1974.
The new particle called the Ds(2317), which combines a
charm quark with another heavy quark called an anti-strange, has
unexpected properties that will provide insight into the force that binds
the quarks together. This force, unlike most others in nature, becomes
stronger as the distance between the two quarks increases.
"The unexpected mass will make us look again at the forces
between quarks and will stimulate new interest in charm-quark systems,"
said Bob Cahn, a BABAR
collaborator from LBNL.
experiment continues to produce important new knowledge, adding to our
fundamental understanding of the structure of matter," said Raymond
Orbach, Director of the DOE Office of Science. "This impressive
accomplishment reflects the success of a strong team of professionals at
SLAC—accelerator physicists, computer specialists, engineers,
administrators and many others—whose efforts were essential for the
result. I would like to congratulate them all on their combined
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