Andrew Yee[_1_]
March 6th 08, 04:40 AM
Fermilab
Media Contacts:
Tona Kunz, Fermilab
630-840-3351
Steve Koppes, University of Chicago
773-702-8366
Kathy Borlik, Indiana University South Bend
574-520-4345
For immediate release: February 14, 2008
08-06
COUPP experiment tightens limits on dark matter
Physicists revive bubble chamber technology to search for WIMPs
Scientists working on the COUPP experiment at the Department of Energy's
Fermi National Accelerator Laboratory today (February 14) announced a new
development in the quest to observe dark matter. The Chicagoland Observatory
for Underground Particle Physics experiment tightened constraints on the
"spin-dependent" properties of WIMPS, weakly interacting massive particles
that are candidates for dark matter. Their results, combined with the
findings of other dark matter searches, contradict the claims for the
observation of such particles by the Dark Matter experiment (DAMA) in Italy
and further restrict the hunting ground for physicists to track their dark
matter quarry.
The COUPP experiment also proved that dusting off an old technology of
particle physics, the bubble chamber, offers extraordinary potential as a
tool in the search for dark matter.
"Our first results are extremely encouraging, and bubble-chamber technology
is eminently scale-able," said Juan Collar, a University of Chicago
professor and spokesman of the COUPP collaboration, which includes 16
scientists and students from the University of Chicago; Indiana University
South Bend; and DOE's Fermilab. "We expect that COUPP will soon have a
sweeping sensitivity to dark matter particles, simultaneously exploring both
spin-dependent and spin-independent mechanisms for dark matter interaction.
This is just one of the aspects that set our experiment apart from the
competition."
Physicists theorize that dark matter particles interact with ordinary matter
via different mechanisms that are either dependent or independent of the
nuclear spin of the atoms in the detector material.
Previous experiments had severely constrained the possibility that the DAMA
observations result from dark matter spin-independent interactions. COUPP
has now ruled out the last region of parameter space that allowed for a
spin-dependent explanation. Several experiments worldwide, including DAMA
itself, had been racing to prove or disprove DAMA's initial claim to observe
WIMPs. If the DAMA result had been due to spin-dependent WIMPs, then COUPP
researchers should have found hundreds of WIMPs. They found none above
background.
The COUPP collaboration details the results in a paper, "Improved
Spin-Dependent WIMP Limits from a Bubble Chamber," appearing in the February
15 issue of the journal Science.
WIMPs, if they exist, rarely interact with ordinary matter. COUPP uses a
glass jar filled with about a liter of iodotrifluoromethane, a
fire-extinguishing liquid known as CF3I, to detect a particle as it hits a
nucleus, triggering evaporation of a small amount of CF3I. The resulting
bubble initially is too small to see but it grows. Using digital cameras,
COUPP scientists study the pictures of bubbles once they reach a millimeter
in size. They look for statistical variations between photographs that
signal whether bubbles were caused by background radiation or by dark
matter.
"Eighty-five percent of the total matter of the universe still eludes direct
detection," said Dennis Kovar, acting associate director for high energy
physics in the DOE Office of Science. "To discover the nature of dark matter
will require both catching dark matter particles with innovative detectors
like COUPP's and making and studying dark matter at particle accelerators."
The COUPP experiment is located 350 feet underground in a tunnel on the
Fermilab site.
"To search for WIMPs, COUPP revived one of the oldest tools in particle
physics: the bubble chamber. As other detector technology surpassed the
bubble chamber in the past two decades, it became nearly extinct in
high-energy physics laboratories," said James Whitmore, NSF program manager.
"Now it is making a comeback in one of the most exciting areas of particle
physics, the search for dark matter."
Other experiments, such as the Cryogenic Dark Matter Search at Fermilab,
look for dark matter underground using a different technology.
"COUPP's use of a bubble chamber is an intriguing technology. It has been
improving its reach for spin-dependent research," said Blas Cabrera,
Stanford University professor and CDMS spokesman. "It is a valuable tool in
the range of technology in the search for dark matter. It is important to
have confirmation from radically different technologies."
"COUPP is a new player in an extremely competitive arena, and it has already
demonstrated it can contribute to the search for dark matter," said Hugh
Montgomery, Fermilab associate director for research. "Now they need to show
whether or not they can take it to the next level."
COUPP aims to increase sensitivity by increasing the amount of liquid from
one liter to 30 liters in the bubble chamber. Physicists expect soon to
start testing the larger chamber at Fermilab. If the larger chamber meets
expectations, the experiment could move to a deeper tunnel to reduce the
background from cosmic radiation even further.
"No one knows for sure if dark matter is made of WIMPs," said Andrew
Sonnenschein, COUPP collaborator. "If it is, we'll have a chance with the
new chamber to find it. That's all we can ask for."
The COUPP collaboration is funded by the National Science Foundation and the
U.S. Department of Energy.
Fermilab is a Department of Energy Office of Science national laboratory
operated under contract by the Fermi Research Alliance, LLC. The DOE Office
of Science is the single largest supporter of basic research in the physical
sciences in the nation.
The National Science Foundation is an independent federal agency that
supports fundamental research and education across all fields of science and
engineering. NSF funds reach all 50 states through grants to more than 1,700
universities and institutions.
Photos are available at:
http://www.fnal.gov/pub/presspass/images/COUPPdarkmattersearch.html
Media Contacts:
Tona Kunz, Fermilab
630-840-3351
Steve Koppes, University of Chicago
773-702-8366
Kathy Borlik, Indiana University South Bend
574-520-4345
For immediate release: February 14, 2008
08-06
COUPP experiment tightens limits on dark matter
Physicists revive bubble chamber technology to search for WIMPs
Scientists working on the COUPP experiment at the Department of Energy's
Fermi National Accelerator Laboratory today (February 14) announced a new
development in the quest to observe dark matter. The Chicagoland Observatory
for Underground Particle Physics experiment tightened constraints on the
"spin-dependent" properties of WIMPS, weakly interacting massive particles
that are candidates for dark matter. Their results, combined with the
findings of other dark matter searches, contradict the claims for the
observation of such particles by the Dark Matter experiment (DAMA) in Italy
and further restrict the hunting ground for physicists to track their dark
matter quarry.
The COUPP experiment also proved that dusting off an old technology of
particle physics, the bubble chamber, offers extraordinary potential as a
tool in the search for dark matter.
"Our first results are extremely encouraging, and bubble-chamber technology
is eminently scale-able," said Juan Collar, a University of Chicago
professor and spokesman of the COUPP collaboration, which includes 16
scientists and students from the University of Chicago; Indiana University
South Bend; and DOE's Fermilab. "We expect that COUPP will soon have a
sweeping sensitivity to dark matter particles, simultaneously exploring both
spin-dependent and spin-independent mechanisms for dark matter interaction.
This is just one of the aspects that set our experiment apart from the
competition."
Physicists theorize that dark matter particles interact with ordinary matter
via different mechanisms that are either dependent or independent of the
nuclear spin of the atoms in the detector material.
Previous experiments had severely constrained the possibility that the DAMA
observations result from dark matter spin-independent interactions. COUPP
has now ruled out the last region of parameter space that allowed for a
spin-dependent explanation. Several experiments worldwide, including DAMA
itself, had been racing to prove or disprove DAMA's initial claim to observe
WIMPs. If the DAMA result had been due to spin-dependent WIMPs, then COUPP
researchers should have found hundreds of WIMPs. They found none above
background.
The COUPP collaboration details the results in a paper, "Improved
Spin-Dependent WIMP Limits from a Bubble Chamber," appearing in the February
15 issue of the journal Science.
WIMPs, if they exist, rarely interact with ordinary matter. COUPP uses a
glass jar filled with about a liter of iodotrifluoromethane, a
fire-extinguishing liquid known as CF3I, to detect a particle as it hits a
nucleus, triggering evaporation of a small amount of CF3I. The resulting
bubble initially is too small to see but it grows. Using digital cameras,
COUPP scientists study the pictures of bubbles once they reach a millimeter
in size. They look for statistical variations between photographs that
signal whether bubbles were caused by background radiation or by dark
matter.
"Eighty-five percent of the total matter of the universe still eludes direct
detection," said Dennis Kovar, acting associate director for high energy
physics in the DOE Office of Science. "To discover the nature of dark matter
will require both catching dark matter particles with innovative detectors
like COUPP's and making and studying dark matter at particle accelerators."
The COUPP experiment is located 350 feet underground in a tunnel on the
Fermilab site.
"To search for WIMPs, COUPP revived one of the oldest tools in particle
physics: the bubble chamber. As other detector technology surpassed the
bubble chamber in the past two decades, it became nearly extinct in
high-energy physics laboratories," said James Whitmore, NSF program manager.
"Now it is making a comeback in one of the most exciting areas of particle
physics, the search for dark matter."
Other experiments, such as the Cryogenic Dark Matter Search at Fermilab,
look for dark matter underground using a different technology.
"COUPP's use of a bubble chamber is an intriguing technology. It has been
improving its reach for spin-dependent research," said Blas Cabrera,
Stanford University professor and CDMS spokesman. "It is a valuable tool in
the range of technology in the search for dark matter. It is important to
have confirmation from radically different technologies."
"COUPP is a new player in an extremely competitive arena, and it has already
demonstrated it can contribute to the search for dark matter," said Hugh
Montgomery, Fermilab associate director for research. "Now they need to show
whether or not they can take it to the next level."
COUPP aims to increase sensitivity by increasing the amount of liquid from
one liter to 30 liters in the bubble chamber. Physicists expect soon to
start testing the larger chamber at Fermilab. If the larger chamber meets
expectations, the experiment could move to a deeper tunnel to reduce the
background from cosmic radiation even further.
"No one knows for sure if dark matter is made of WIMPs," said Andrew
Sonnenschein, COUPP collaborator. "If it is, we'll have a chance with the
new chamber to find it. That's all we can ask for."
The COUPP collaboration is funded by the National Science Foundation and the
U.S. Department of Energy.
Fermilab is a Department of Energy Office of Science national laboratory
operated under contract by the Fermi Research Alliance, LLC. The DOE Office
of Science is the single largest supporter of basic research in the physical
sciences in the nation.
The National Science Foundation is an independent federal agency that
supports fundamental research and education across all fields of science and
engineering. NSF funds reach all 50 states through grants to more than 1,700
universities and institutions.
Photos are available at:
http://www.fnal.gov/pub/presspass/images/COUPPdarkmattersearch.html