No Dark Matter Down Here

A mile deep in the earth, the most sensitive search to date for dark matter has turned up nothing.

Today, scientists announced negative results for a test of dark matter deep in South Dakota mine, Live Science reported.  Scientists with the LUX (Large Underground Xenon) Dark Matter Detector – years in the making, largest of its kind in the world in the deepest gold mine in North America – hoped to “strike gold” with the sensitive instrument, according to an article from National Public Radio (NPR) last August 2012.  “There’s lots riding on this race” to find dark matter, they said – lots of federal funding, too, to run it (about $1 million a month).  Researchers were hoping for a Nobel-Prize-class discovery.

The LUX detector is outfitted to look for WIMPs (Weakly Interacting Massive Particles), theoretical subatomic particles with large mass that bypass ordinary matter except for weak gravitational interactions.  Along with MACHOs (Massive Compact Halo Objects, planet-size matter, 7/20/12), WIMPs are a variety of “cold dark matter” as opposed to the “hot dark matter” of neutrinos.  WIMPs are “thought to be the leading candidates for the particles that make up dark matter,” Live Science said.  If they exist, they would permeate all space, passing through our bodies with nary a nudge.  The combined gravity of uncounted numbers of these particles could, it was believed, allow clumps from the Big Bang to condense into stars and galaxies, according to the most popular models.  Without that extra gravity, models could not account for the “lumpiness” of the universe.

The South Dakota mine has been confirmed as the “quietest place verified in the world,” therefore ideal for finding the elusive particles if they exist.  Gravitational contacts with xenon atoms could release flashes of light toward the detectors.  The LUX experiment failed to verify potential detections of WIMPs from other, less sensitive instruments. Based on those hopeful hints, scientists expected to find 1,600 flashes.  “No such signals were seen.”  (See 7/30/09.)

The non-detection puts WIMPs in a bind, New Scientist wrote.  “That may spell trouble for elegant recent theories of a shadow universe where myriad particles interact via their own dark forces.”  While not a complete falsification (since WIMPs may be “even wimpier than assumed”), the researchers felt they had spread a “big net” for them.  “I’m afraid that these light WIMP models for us seem to be dead,” says LUX team member Richard Gaitskell of Brown University in Rhode Island.  This material is from: crev.info.

According to current big bang models, dark matter and dark energy make up 95% of the “mysterious unknown stuff” (MUST) of the universe.  Nobel laureate Saul Perlmutter said, “The universe’s mysterious dark sector presents us with two of the most thrilling challenges in all of physics.”  Dark energy remains completely unknown (10/21/12).  Dark matter has failed several empirical tests.  Instead of the thrill of victory, so far it has been the agony of defeat.

Speaking of dark energy, “perhaps the most important problem in cosmology today,” Nature wrote that astronomers are now using “fake data” in their contest to find it.  Why?  “We’re focusing on questions that are difficult to address in real data.”   It’s kind of a double-blind test, where the astronomers don’t know if they’re using fake or real data in their detection methods.  Since there are no real data identifying dark energy, though, one can ask if that is a distinction without a difference.

Update 2/21/14:  Improved calibration of the LUX detector by a factor of 10 confirms the result, Science Daily said: no WIMPs were detected.

Sorry, guys.  Tough luck.  Suggestion: Instead of hunting for ghosts (7/23/07), whistling in the dark (4/28/13), or using occult forces as escape hatches (5/14/12), how about considering creation? (2/28/08).  It’s not wise to love dark matter rather than light (12/31/11).