Andrew Yee[_1_]
March 6th 08, 04:32 AM
Public Affairs Office
University of California-Santa Barbara
Contacts:
Gail Gallessich, 805-893-7220
Kurt Riesselmann, 630-840-5681
Featured researchers:
Harry Nelson
805-893-8612 / 805-729-0059
February 25, 2008
U.S. Experiment Retakes the Lead in Race To Find Dark Matter
Santa Barbara, Calif. -- Scientists of the Cryogenic Dark Matter Search
experiment today announced that they have regained the lead in the worldwide
race to find the particles that make up dark matter. The CDMS experiment,
conducted a half-mile underground in a mine in Soudan, Minn., again sets the
world's best constraints on the properties of dark matter candidates.
Dark matter is thought to comprise about one-fifth of the energy in the
universe, and 85 percent of all matter in the universe. Matter made of
neutrons, protons, and electrons makes up the other 15 percent of matter in
the universe.
Teams searching for dark matter have quadrupled in the past few years, now
numbering 20. UC Santa Barbara is among 16 institutions involved in the CDMS
experiment. UCSB emeritus professor David Caldwell, a physicist, was one of
the originators of the experiment.
On Friday, February 22, results from the CDMS experiment were presented at
the "Eighth UCLA Symposium: Sources and Detection of Dark Matter and Dark
Energy in the Universe," held in Marina del Ray. Rupak Mahapatra, project
scientist at UCSB, presented the data from the CDMS experiment. A scientific
paper describing the work was posted simultaneously on the public CDMS
experiment website at:
http://cdms.berkeley.edu/index.html
The roomful of approximately 200 scientists from around the world erupted in
wild applause during and after Mahapatra's presentation. He showed that no
signal has yet been detected, but the experiment is now considered the most
sensitive in the world. The germanium crystals used as detectors in the
underground mine have been increased by a factor of three in mass. Mahapatra
led the data analysis effort for the current announcement.
"The Big Bang and current observations suggest that the dark matter is
related to the 'Weak Interaction,' which governs certain radioactive decays,
like the decay of potassium that is in bananas and people's bones," said
Harry Nelson, professor of physics at UC Santa Barbara and one of the
principal investigators in the experiment. "Dark matter is also thought to
consist of a massive particle, about 100 times the mass of a proton. These
two concepts together make up the name of the particle that CDMS is looking
for, the 'WIMP,' for Weakly Interacting Massive Particle."
Nelson explained that the experiment uses a "billiard ball" scattering
technique to seek evidence for WIMPs. It is as though the WIMP is the cue
ball, and germanium atoms are the pool balls. "We can't see the WIMP
directly, but our sensors can detect the sound, like a ring of a bell, if a
germanium atom suddenly gets struck by a WIMP," he said.
Blas Cabrera of Stanford University is co-spokesperson of the CDMS
experiment, and the Department of Energy's Fermi National Accelerator
Laboratory hosts the project's management. "With our new result we are
leapfrogging the competition," said Cabrera. "We have achieved the world's
most stringent limits on how often dark matter particles interact with
ordinary matter and how heavy they are, in particular in the theoretically
favored mass range of more than 40 times the proton mass. Our experiment is
now sensitive enough to hear WIMPs even if they ring the 'bells' of our
crystal germanium detector only twice a year. So far, we have heard
nothing."
WIMPs, are leading candidates for the building blocks of dark matter.
Hundreds of billions of WIMPs may have passed through your body as you read
these sentences.
If they exist, WIMPs might interact with ordinary matter at rates similar to
those of low-energy neutrinos, elusive subatomic particles first proposed in
the 1930's. The CDMS collaboration found that if WIMPs have 100 times the
mass of protons, they collide with one kilogram of germanium less than a few
times per year; otherwise, the CDMS experiment would have detected them.
"The nature of dark matter is one of the mysteries in particle physics and
cosmology," said Dr. Dennis Kovar, Acting Associate Director for High Energy
Physics in the U.S. Department of Energy's Office of Science.
"Congratulations to the CDMS collaboration for improved sensitivity and a
new limit in the search for dark matter."
The CDMS experiment is located in the Soudan Underground Laboratory,
shielded from cosmic rays and other particles that could mimic the signals
expected from dark matter particles. Scientists operate the ultra sensitive
CDMS detectors under clean-room conditions at a temperature of about 40
millikelvin, close to absolute zero. Physicists expect that WIMPs, if they
exist, travel right through ordinary matter, rarely leaving a trace. If
WIMPs crossed the CDMS detector, occasionally one of the WIMPs would hit a
germanium nucleus. Like a hammer hitting a bell, the collision would create
vibrations of the detector's crystal grid, which scientists could detect.
Not having observed such signals, the CDMS experiment set limits on the
properties of WIMPs.
"Observations made with telescopes have repeatedly shown that dark matter
exists. It is the stuff that holds together all cosmic structures, including
our own Milky Way. The observation of WIMPs would finally reveal the
underlying nature of this dark matter, which plays such a crucial role in
the formation of galaxies and the evolution of our universe," said Joseph
Dehmer, director of the Division of Physics for the National Science
Foundation.
The discovery of WIMPs would require extensions to the theoretical framework
known as the Standard Model of particles and their forces. Mahapatra's
presentation to the scientific community at the symposium Feb. 22 tests the
viability of new theoretical concepts that have been proposed.
"Our results constrain theoretical models such as supersymmetry and models
based on extra dimensions of space-time, which predict the existence of
WIMPs," said CDMS project manager Dan Bauer, of the Department of Energy's
Fermilab. "For WIMP masses expected from these theories, we are again the
most sensitive in the world, retaking the lead from the Xenon 10 experiment
at the Italian Gran Sasso laboratory. We will gain another factor of three
in sensitivity by continuing to take more data with our detector in the
Soudan laboratory until the end of 2008."
A new phase of the CDMS experiment with 25 kilograms of germanium is planned
for the SNOLAB facility in Canada.
"The 25-kilogram experiment has clear discovery potential," said Fermilab
Director Pier Oddone. "It covers a lot of the territory predicted by
supersymmetric theories."
The CDMS collaboration includes more than 50 scientists from 16 institutions
and receives funding from the U.S. Department of Energy, the National
Science Foundation and from member institutions, including collaborators
from Canada. The UCSB group receives its funding through the university
program of the U.S. Department of Energy.
Fermilab is a DOE 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.
NSF 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.
Institutions participating in CDMS are Case Western Reserve University;
Fermi National Accelerator Laboratory; Lawrence Berkeley National
Laboratory; Massachusetts Institute of Technology; Queens University, Santa
Clara University; Stanford University; Syracuse University; University of
California, Berkeley; University of California, Santa Barbara; University of
Colorado Denver; University of Florida; University of Minnesota; Brown
University; the California Institute of Technology; and the University of
Zurich.
Related links:
* Cryogenic Dark Matter Search
http://cdms.berkeley.edu/index.html
* CDMS photos and videos
http://www.fnal.gov/pub/presspass/press_releases/CDMS_Photos2008/index.html
* Background on dark matter
http://www.fnal.gov/pub/presspass/press_releases/cdms_background2008.html
University of California-Santa Barbara
Contacts:
Gail Gallessich, 805-893-7220
Kurt Riesselmann, 630-840-5681
Featured researchers:
Harry Nelson
805-893-8612 / 805-729-0059
February 25, 2008
U.S. Experiment Retakes the Lead in Race To Find Dark Matter
Santa Barbara, Calif. -- Scientists of the Cryogenic Dark Matter Search
experiment today announced that they have regained the lead in the worldwide
race to find the particles that make up dark matter. The CDMS experiment,
conducted a half-mile underground in a mine in Soudan, Minn., again sets the
world's best constraints on the properties of dark matter candidates.
Dark matter is thought to comprise about one-fifth of the energy in the
universe, and 85 percent of all matter in the universe. Matter made of
neutrons, protons, and electrons makes up the other 15 percent of matter in
the universe.
Teams searching for dark matter have quadrupled in the past few years, now
numbering 20. UC Santa Barbara is among 16 institutions involved in the CDMS
experiment. UCSB emeritus professor David Caldwell, a physicist, was one of
the originators of the experiment.
On Friday, February 22, results from the CDMS experiment were presented at
the "Eighth UCLA Symposium: Sources and Detection of Dark Matter and Dark
Energy in the Universe," held in Marina del Ray. Rupak Mahapatra, project
scientist at UCSB, presented the data from the CDMS experiment. A scientific
paper describing the work was posted simultaneously on the public CDMS
experiment website at:
http://cdms.berkeley.edu/index.html
The roomful of approximately 200 scientists from around the world erupted in
wild applause during and after Mahapatra's presentation. He showed that no
signal has yet been detected, but the experiment is now considered the most
sensitive in the world. The germanium crystals used as detectors in the
underground mine have been increased by a factor of three in mass. Mahapatra
led the data analysis effort for the current announcement.
"The Big Bang and current observations suggest that the dark matter is
related to the 'Weak Interaction,' which governs certain radioactive decays,
like the decay of potassium that is in bananas and people's bones," said
Harry Nelson, professor of physics at UC Santa Barbara and one of the
principal investigators in the experiment. "Dark matter is also thought to
consist of a massive particle, about 100 times the mass of a proton. These
two concepts together make up the name of the particle that CDMS is looking
for, the 'WIMP,' for Weakly Interacting Massive Particle."
Nelson explained that the experiment uses a "billiard ball" scattering
technique to seek evidence for WIMPs. It is as though the WIMP is the cue
ball, and germanium atoms are the pool balls. "We can't see the WIMP
directly, but our sensors can detect the sound, like a ring of a bell, if a
germanium atom suddenly gets struck by a WIMP," he said.
Blas Cabrera of Stanford University is co-spokesperson of the CDMS
experiment, and the Department of Energy's Fermi National Accelerator
Laboratory hosts the project's management. "With our new result we are
leapfrogging the competition," said Cabrera. "We have achieved the world's
most stringent limits on how often dark matter particles interact with
ordinary matter and how heavy they are, in particular in the theoretically
favored mass range of more than 40 times the proton mass. Our experiment is
now sensitive enough to hear WIMPs even if they ring the 'bells' of our
crystal germanium detector only twice a year. So far, we have heard
nothing."
WIMPs, are leading candidates for the building blocks of dark matter.
Hundreds of billions of WIMPs may have passed through your body as you read
these sentences.
If they exist, WIMPs might interact with ordinary matter at rates similar to
those of low-energy neutrinos, elusive subatomic particles first proposed in
the 1930's. The CDMS collaboration found that if WIMPs have 100 times the
mass of protons, they collide with one kilogram of germanium less than a few
times per year; otherwise, the CDMS experiment would have detected them.
"The nature of dark matter is one of the mysteries in particle physics and
cosmology," said Dr. Dennis Kovar, Acting Associate Director for High Energy
Physics in the U.S. Department of Energy's Office of Science.
"Congratulations to the CDMS collaboration for improved sensitivity and a
new limit in the search for dark matter."
The CDMS experiment is located in the Soudan Underground Laboratory,
shielded from cosmic rays and other particles that could mimic the signals
expected from dark matter particles. Scientists operate the ultra sensitive
CDMS detectors under clean-room conditions at a temperature of about 40
millikelvin, close to absolute zero. Physicists expect that WIMPs, if they
exist, travel right through ordinary matter, rarely leaving a trace. If
WIMPs crossed the CDMS detector, occasionally one of the WIMPs would hit a
germanium nucleus. Like a hammer hitting a bell, the collision would create
vibrations of the detector's crystal grid, which scientists could detect.
Not having observed such signals, the CDMS experiment set limits on the
properties of WIMPs.
"Observations made with telescopes have repeatedly shown that dark matter
exists. It is the stuff that holds together all cosmic structures, including
our own Milky Way. The observation of WIMPs would finally reveal the
underlying nature of this dark matter, which plays such a crucial role in
the formation of galaxies and the evolution of our universe," said Joseph
Dehmer, director of the Division of Physics for the National Science
Foundation.
The discovery of WIMPs would require extensions to the theoretical framework
known as the Standard Model of particles and their forces. Mahapatra's
presentation to the scientific community at the symposium Feb. 22 tests the
viability of new theoretical concepts that have been proposed.
"Our results constrain theoretical models such as supersymmetry and models
based on extra dimensions of space-time, which predict the existence of
WIMPs," said CDMS project manager Dan Bauer, of the Department of Energy's
Fermilab. "For WIMP masses expected from these theories, we are again the
most sensitive in the world, retaking the lead from the Xenon 10 experiment
at the Italian Gran Sasso laboratory. We will gain another factor of three
in sensitivity by continuing to take more data with our detector in the
Soudan laboratory until the end of 2008."
A new phase of the CDMS experiment with 25 kilograms of germanium is planned
for the SNOLAB facility in Canada.
"The 25-kilogram experiment has clear discovery potential," said Fermilab
Director Pier Oddone. "It covers a lot of the territory predicted by
supersymmetric theories."
The CDMS collaboration includes more than 50 scientists from 16 institutions
and receives funding from the U.S. Department of Energy, the National
Science Foundation and from member institutions, including collaborators
from Canada. The UCSB group receives its funding through the university
program of the U.S. Department of Energy.
Fermilab is a DOE 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.
NSF 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.
Institutions participating in CDMS are Case Western Reserve University;
Fermi National Accelerator Laboratory; Lawrence Berkeley National
Laboratory; Massachusetts Institute of Technology; Queens University, Santa
Clara University; Stanford University; Syracuse University; University of
California, Berkeley; University of California, Santa Barbara; University of
Colorado Denver; University of Florida; University of Minnesota; Brown
University; the California Institute of Technology; and the University of
Zurich.
Related links:
* Cryogenic Dark Matter Search
http://cdms.berkeley.edu/index.html
* CDMS photos and videos
http://www.fnal.gov/pub/presspass/press_releases/CDMS_Photos2008/index.html
* Background on dark matter
http://www.fnal.gov/pub/presspass/press_releases/cdms_background2008.html