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World’s most sensitive detector hunts for dark matter

Tuesday, Dec 15, 2015,16:35 IST By Metrovaartha A A A

Washington | A new set of calibration techniques have been employed upon the world’s most sensitive dark matter detector that is hunting for the unseen stuff believed to account for most of the matter in the universe.

Researchers with The Large Underground Xenon (LUX) are looking for Weakly Interacting Massive Particles (WIMPs) 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, a professor at Brown University in US.

It is vital that we continue to push the capabilities of our detector in the search for the elusive dark matter particles, Gaitskell said.

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.

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, Currie said.

LUX consists of one-third tonne 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. So far LUX has not 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. One calibration technique used neutrons as stand-ins for dark matter particles.

Bouncing neutrons off the xenon atoms allows scientists to quantify how the LUX detector responds to the recoiling process. It is like a giant game of pool with a neutron as the cue ball and the xenon atoms as the stripes and solids, said Gaitskell.

We can track the neutron to deduce the details of the xenon recoil, and calibrate the response of LUX better than anything previously possible, he said.

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