The Large Underground Xenon (LUX) dark matter experiment, which operates nearly a mile underground at the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota, has already proven itself to be the most sensitive detector in the hunt for dark matter, the
unseen stuff believed to account for
most of the matter in the universe. Now, a new set of calibration techniques employed by LUX scientists has again
dramatically improved the detector's sensitivity.
Researchers with
LUX are looking for WIMPs, or weakly interacting massive particles, which are among the
leading candidates for dark matter. "We have improved the sensitivity of LUX by more than a factor of 20 for low-mass dark
matter particles, significantly enhancing our ability to look for WIMPs," said Rick Gaitskell, professor of physics at Brown University and co-spokesperson for the LUX experiment.
"It is vital that we continue to push the capabilities of our detector in the search for the elusive dark matter particles," Gaitskell said.
LUX improvements, coupled to advanced computer simulations at the U.S. Department of Energy's Lawrence Berkeley National Laboratory's (Berkeley Lab) National Energy Research Scientific Computing Center (NERSC) and Brown University's Center for Computation and Visualization (CCV), have allowed scientists to test additional particle models of dark matter
that now can be excluded from the search. NERSC also stores large volumes of LUX data—measured in trillions of bytes, or terabytes—and Berkeley Lab has a growing role in the LUX collaboration.
Scientists are
confident that dark matter exists
because the
effects of its gravity can be seen in the rotation of galaxies and in the way light bends as it travels through the universe. Because WIMPs
are thought to interact with other matter only on very rare occasions,
they have yet to be detected directly.
"We have looked for dark matter particles during the experiment's first three-month run, but are exploiting new calibration techniques better pinning down how they would appear to our detector," said Alastair Currie of Imperial College London, a LUX researcher. "These calibrations have deepened our understanding of the response of xenon to dark matter, and to backgrounds. This allows us to search, with improved confidence, for particles that we hadn't previously known would be visible to LUX."
The new research is described in a paper submitted to Physical Review Letters. The work reexamines data collected during LUX's first three-month run in 2013 and helps to rule out the possibility of dark matter detections at low-mass ranges where other experiments had previously reported potential detections.
LUX consists of one-third ton of liquid xenon surrounded with sensitive light detectors. It is designed to identify the very rare occasions when a dark matter particle collides with a xenon atom inside the detector. When a collision happens, a xenon atom will recoil and emit a tiny flash of light, which is detected by LUX's light sensors. The detector's location at Sanford Lab beneath a mile of rock helps to shield it from cosmic rays and other radiation that would interfere with a dark matter signal.
So far LUX hasn't detected a dark matter signal, but its exquisite sensitivity has allowed scientists to
all but rule out vast mass ranges where dark matter particles might exist. These new calibrations increase that sensitivity even further.....