Tuesday, October 21, 2014
YOLO COUNTY NEWS
99 CENTS

Team crosses off dark matter particle candidates

By
From page A7 | December 11, 2013 |

Results from the first run of the Large Underground Xenon experiment, operating a mile underground in the Black Hills of South Dakota, have proven the detector’s sensitivity and ruled out some possible candidates for a dark matter particle.

Initial results from 85 days worth of accumulated data were announced last month at a seminar at the Sanford Underground Research Facility in Lead, S.D.

“LUX is already producing the world’s best results and excluding parameter space for a dark matter particle,” said Matthew Szydagis, a postdoctoral researcher at the UC Davis department of physics. Szydagis is responsible for coordinating data analysis among the members of the LUX team.

Mani Tripathi, a UCD physics professor, is one of the seven founding principal investigators who proposed the LUX experiment in 2006. “We are finally seeing the fruits of our labor after these many years,” he said.

Dark matter is the most abundant form of matter in the universe but has so far been inferred only by its gravitational effects on light from distant galaxies and clusters of galaxies.

The leading theoretical candidates for a dark matter particle are WIMPs, or weakly interacting massive particles — so-called because they are postulated to interact ever so feebly with ordinary matter.

LUX was designed to have greater sensitivity to detect WIMPs than any other existing experiment. Recently, other researchers using ultra-cold silicon detectors reported three candidate WIMP events. However, these WIMPs would have produced more than 1,600 events in LUX’s much larger detector, or one every 80 minutes in the recent run. No such signals were seen.

“This is only the beginning for LUX,” said Dan McKinsey, a physicist at Yale University and co-spokesperson for the project. “Now that we understand the instrument and its backgrounds, we will continue to take data, testing for more and more elusive candidates for dark matter.”

In both theory and practice, collisions between WIMPs and normal matter are rare and extremely difficult to detect, especially because a constant rain of cosmic radiation from space can drown out the faint signals.

That’s why LUX is searching for WIMPs 4,850 feet underground in the Sanford Lab, where few cosmic ray particles can penetrate. The detector is further protected from background radiation from the surrounding rock by immersion in a tank of ultra-pure water, which was designed and instrumented by the UCD team.

At the heart of the experiment is a 6-foot-tall titanium tank filled with about a third of a ton of liquid xenon, cooled to minus 150 degrees Fahrenheit. If a WIMP strikes a xenon atom, it recoils from other xenon atoms and emits photons (light) and electrons.

The electrons are drawn upward by an electrical field and interact with a thin layer of xenon gas at the top of the tank, releasing more photons.

Light detectors in the top and bottom of the tank are each capable of detecting a single photon, so the locations of the two photon signals — one at the collision point, the other at the top of the tank — can be pinpointed to within a few millimeters. The energy of the interaction can be precisely measured from the brightness of the signals.

Installed in the summer of 2012, the experiment was filled with liquid xenon in February, and its first run of three months was conducted this spring and summer, followed by intensive analysis of the data. The dark matter search will continue through the next two years.

The Sanford Lab is a state-owned facility, and the U.S. Department of Energy supports its operation. The LUX scientific collaboration, supported by the National Science Foundation and DOE, includes 17 research universities and national laboratories in the U.S., the United Kingdom and Portugal.

UCD physicists contributed strongly to all aspects of LUX: design, construction, installation, commissioning, calibration, operations and data analysis.

Electronics engineer Britt Holbrook, and graduate students Mike Woods and Sergey Uvarov, played leading roles in the areas of electronics and computing. Mechanical engineer John Thomson and graduate student Jeremy Mock oversaw the installation of mechanical supports and the tricky move of the assembled detector to the underground lab.

The group was a leader in simulations, with key contributions from Szydagis, and graduate students Melinda Sweany and Nick Walsh. About 20 UC undergraduates have worked on LUX over the past seven years.

Planning for the next-generation dark matter experiment at the Sanford Lab already is under way. Compared to LUX’s third of a ton of liquid xenon, the LUX-ZEPLIN, or LZ, experiment would have a 7-ton liquid xenon target inside the same 72,000-gallon tank of pure water used by LUX and a sensitivity about a thousand times higher.

LUX and LZ are among 14 active research groups at the Sanford Lab. Other teams of researchers are planning experiments in physics, geology and biology that could extend the future of the lab for decades.

— UC Davis News

Comments

comments

.

News

Winters homicide case enters jury-selection phase

By Lauren Keene | From Page: A1

 
So much more than a cute baby store

By Bob Schultz | From Page: A1 | Gallery

 
Suspected arson fires worry neighbors, firefighters

By Lauren Keene | From Page: A1 | Gallery

 
Fill the Boot for the hungry

By Enterprise staff | From Page: A2

Existing home sales rise in September

By The Associated Press | From Page: A2

 
For the record

By Enterprise staff | From Page: A2

Democrats love seeing minimum wage on the ballot

By The Associated Press | From Page: A2

 
Pets of the week

By Enterprise staff | From Page: A2 | Gallery

 
Apply now for community mediation training

By Enterprise staff | From Page: A3

Paws for Thought: Pets for Vets: matches made in heaven

By Evelyn Dale | From Page: A3 | Gallery

 
‘Tokyo Kill’ author will visit bookstore

By Special to The Enterprise | From Page: A3

Sierra Club gathers for morning walks

By Special to The Enterprise | From Page: A3

 
DPNS has play group, preschool openings

By Enterprise staff | From Page: A3

Yolo Knitters Guild plans fall meetings

By Enterprise staff | From Page: A3

 
Local farm products found at hospital market

By Enterprise staff | From Page: A3

Tax tips offered for sole proprietors

By Enterprise staff | From Page: A3

 
First-time home buyers get free advice

By Enterprise staff | From Page: A4

Psychiatric clinic hosts open house

By Enterprise staff | From Page: A4

 
Beer dinner set on Co-op patio

By Enterprise staff | From Page: A4

Walkin’ the Dawg through the park

By Enterprise staff | From Page: A4 | Gallery

 
 
Essay contest winners will be honored Tuesday

By Special to The Enterprise | From Page: A4

Volunteers sought to make veggie bags

By Enterprise staff | From Page: A4

 
Library hosts after-hours teen movie nights

By Enterprise staff | From Page: A4

Forum eyes impacts of raising the local minimum wage

By Special to The Enterprise | From Page: A5

 
NAMI-Yolo family support group meets Sunday

By Enterprise staff | From Page: A7

To save the birds, look to the fish

By Kat Kerlin | From Page: A7 | Gallery

 
Birding field trip planned Saturday

By Enterprise staff | From Page: A12 | Gallery

.

Forum

Ready to go, whatever happens

By Creators Syndicate | From Page: B5

 
Where there’s a will …

By Creators Syndicate | From Page: B5

Archer, Nolan are my picks

By Letters to the Editor | From Page: A8

 
She’s innovative, passionate

By Letters to the Editor | From Page: A8

An accidental fan becomes a baseball devotee

By Special to The Enterprise | From Page: A8

 
U.N. steps up to lead Ebola response

By Special to The Enterprise | From Page: A8

John Cole cartoon

By Debbie Davis | From Page: A8

 
These three are the best

By Letters to the Editor | From Page: A8

Sunder has bold vision

By Letters to the Editor | From Page: A8

 
.

Sports

UCD’s Wegener is the engine that drives the train

By Bruce Gallaudet | From Page: B1 | Gallery

 
Villegas wonderstrike powers Devils

By Evan Ream | From Page: B1 | Gallery

DHS golfers take the title

By Enterprise staff | From Page: B1

 
Devil defense regresses in football loss

By Thomas Oide | From Page: B1

Sports briefs: Top-end tennis talent helps DHS girls grab a win

By Enterprise staff | From Page: B2 | Gallery

 
Junior Blue Devils: Regular slate ends with 2 Davis teams playoff bound

By Enterprise staff | From Page: B3 | Gallery

After running the gridiron gauntlet, can UCD regroup?

By Bruce Gallaudet | From Page: B8 | Gallery

 
.

Features

.

Arts

 
Stories on Stage Davis presents tales by Lescroart, Montieth

By Special to The Enterprise | From Page: A11 | Gallery

 
.

Business

.

Obituaries

Peggy Belenis Swisher

By Special to The Enterprise | From Page: A4

 
.

Comics

Comics: Tuesday, October 21, 2014 (set 1)

By Creator | From Page: B5

 
Comics: Tuesday, October 21, 2014 (set 2)

By Creator | From Page: B7