Science & Technology

LUX Dark Matter Detector Completes First 90-Days of Operation

Photomultiplier tubes succesful of detecting a single photon of mild line the highest and backside of the LUX darkish matter detector. They may file the place and depth of collisions between darkish matter particles and xenon nuclei. Credit score: Photographs by Matt Kapust/Sanford Underground Analysis Facility

With its first 90-days of operation accomplished, researchers on the Giant Underground Xenon experiment are reporting that LUX has demonstrated a sensitivity that’s higher than any earlier experiment trying to detect darkish matter particles immediately.

Windfall, Rhode Island (Brown College) — In its first three months of operation, the Giant Underground Xenon (LUX) experiment has confirmed itself to be probably the most delicate darkish matter detector on the earth, scientists with the experiment introduced at this time.

“LUX is blazing the trail to illuminating the character of darkish matter,” Rick Gaitskell, professor of physics at Brown College and co-spokesperson for LUX. The detector’s location, greater than a mile underground on the Sanford Underground Analysis Facility in South Dakota, gives a “supremely quiet” atmosphere to detect the uncommon, weak interactions between darkish matter particles and peculiar matter, Gaitskell mentioned.

The primary outcomes from the experiment’s preliminary 90-day run have been introduced at this time throughout a seminar on the Sanford Lab in Lead, S.D.

“What we’ve performed in these first three months of operation is take a look at how nicely the detector is performing, and we’re extraordinarily happy with what we’re seeing,” mentioned Gaitskell, one of the founders of the LUX experiment. “This primary run demonstrates a sensitivity that’s higher than any earlier experiment trying to detect darkish matter particles immediately.”

With LUX’s preliminary run full, the crew will now make a number of changes to fine-tune the system’s sensitivity in anticipation of a brand new 300-day run to start in 2014.

The LUX detector is lined with white teflon to higher collect faint alerts of mild that will likely be recorded by the photomultiplier tubes. Water — 70,000 gallons of it — offers additional safety from background radiation.

Dark matter is assumed to account for as a lot as 85 % of the matter within the universe. However as a result of it hardly ever interacts with different kinds of matter, it has but to be detected immediately. The main candidates for darkish matter particles are referred to as weakly interacting huge particles — WIMPS.

Concept and experimental outcomes recommend that WIMPs may take both a high-mass or low-mass kind. Within the seek for high-mass WIMPs weighing 40 instances the mass of a proton, LUX has twice the sensitivity of some other darkish matter direct-detection experiment, in response to these new outcomes. LUX additionally has vastly enhanced sensitivity to low-mass WIMPs, and new outcomes recommend that potential detections of low-mass WIMPS by different darkish matter experiments have been doubtless the consequence of background radiation, not darkish matter.

“There have been a quantity of darkish matter experiments over the previous few years which have strongly supported the concept that they’re seeing occasions within the lowest vitality bins of their detectors that may very well be in step with the invention of darkish matter,” Gaitskell mentioned. “With the LUX, we’ve got labored very laborious to calibrate the efficiency of the detector in these lowest vitality bins, and we’re not seeing any proof of darkish matter particles there.”

Within the upcoming 300-day run, the LUX researchers hope both to detect darkish matter definitively or to rule out an enormous swath of parameter house the place it may be discovered.

“Daily that we run a detector like this we’re probing new fashions of darkish matter,” Gaitskell mentioned. “That’s extraordinarily essential as a result of we don’t but perceive the universe nicely sufficient to know which of the fashions is definitely the right one. LUX helps to pin that down.”

Elusive particles

Although darkish matter has not but been detected immediately, scientists are pretty sure that it exists. With out its gravitational affect, galaxies and galaxy clusters would merely fly aside into the vastness of house. However as a result of darkish matter doesn’t emit or replicate mild, and its interactions with different kinds of matter are vanishingly uncommon, it’s exceedingly troublesome to identify.

“To offer some concept of how small the likelihood of having a darkish matter particle work together, think about firing one darkish matter particle right into a block of lead,” Gaitskell mentioned. “With the intention to get a 50-50 probability of the particle interacting with the lead, the block would wish to stretch for about 200 mild years — that is 50 instances farther than the closest star to the Earth except for the solar. So it’s an extremely uncommon interplay.”

Capturing these interactions requires an extremely delicate detector. The important thing half of the LUX is a 3rd of a ton of supercooled xenon in a tank festooned with mild sensors, every succesful of detecting a single photon at a time. When a particle interacts with the xenon, it creates a tiny flash of mild and an ion cost, each of that are picked up by the sensors.

To attenuate extraneous interactions not on account of darkish matter, the detector have to be shielded from background radiation and cosmic rays. For that purpose, the LUX is positioned 4,850 ft underground, submerged in 71,600 gallons of pure de-ionized water.

However even in that fortress of solitude, occasional background interactions nonetheless occur. It’s the job of LUX physicists to separate the sign from the noise.

Watching interactions, one after the other

Throughout its preliminary run, the LUX picked up xenon flashes within the vitality area of curiosity for darkish matter at a fee of about one per day. By trying fastidiously on the nature of every interplay, the researchers can inform which of them are from residual background radiation and which may very well be on account of darkish matter.

“Dark matter will work together with the nucleus of xenon atom, whereas most kinds of radioactive background are inclined to work together with the outer electrons,” Gaitskell defined. “Every of these interactions produces a recoil, both of the nucleus or the electrons. So on the fee of about one a day, we see these interactions and take a look at to see if they’re in step with a nuclear recoil or an electron recoil. To date each occasion we’ve got seen has seemed like a traditional electromagnetic background occasion.”

However because the detector runs for longer intervals, the percentages {that a} darkish matter interplay will likely be captured improve. And the LUX, says Gaitskell, has the sensitivity to catch it.

“LUX is a big step ahead. Throughout the first couple of minutes of switching it on, we surpassed the sensitivity of the primary darkish matter detectors I used to be concerned with 25 years in the past,” he mentioned. “Inside a number of days, it surpassed the sensitivity of sum complete of all earlier darkish matter direct search experiments I’ve ever labored on. This primary LUX run is extra delicate than any earlier search performed and now units us up completely for the 300-day run to comply with.”

Collaborative effort

The LUX scientific collaboration contains 17 analysis universities and nationwide laboratories in america, the UK, Portugal, and Russia. The work is supported by the U.S. Division of Vitality and the State of South Dakota. At Brown, 18 postdoctoral researchers, graduate college students, and undergraduates have labored on the challenge.

Brown College analysis affiliate Simon Fiorucci, postdoctoral researcher Monica Pangilinan, and graduate college students Jeremy Chapman, David Malling, and Carlos Faham have been engaged on the LUX challenge since its inception. Fiorucci is now the science coordination supervisor for the challenge and has been instrumental in delivering the brand new science. Chapman and Malling’s Brown College theses comprise the first evaluation used for this newest consequence. “We’re very excited that our thesis work has culminated on this world-leading consequence,” Chapman mentioned.

“Assist from the administration at Brown was instrumental within the LUX getting the experiment off the bottom and enabling us to take care of a number one place within the experiment.” Gaitskell mentioned. “The Brown group has been extraordinarily essential to creating this experiment be the success that it’s.”

Picture: Matt Kapust/Sanford Underground Analysis Facility

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