World’s Most Sensitive Dark Matter Detector Gets a Boost

There is still no detection of individual dark matter particles. Really, there couldn’t be. As reported in the paper submitted to Physical Review Letters, this latest work was simply doing a better job of calibrating the detector to better understand the two light signals produced, in turn to better reject the background from non-WIMP particles interacting in the xenon, of which there are many. Finding WIMPS amounts to searching for a very small needle in a huge haystack.



The LUX scientists are now able to sift that haystack a little more thoroughly, leading to an increasingly stringent upper limit on the physical parameter space these particles could occupy. When applied to a 2013 observation run, this calibration work has significantly increased the sensitivity to low-mass WIMPs that have been the source of potential detections by others in the past.

The story of our attempt to understand dark matter is a long one with Fritz Zwicky in 1933 measuring velocities of galaxies in clusters that were so high the clusters should have flown apart. Vera Rubin and her team in 1978 showed that the velocities of stars in individual galaxies should do the same for galaxies if the stars were not held in orbit by a stronger gravitational force than could be accounted for by the matter emitting visible light. At that point, the hunt for dark matter particles was on; it has produced confusing and potentially contradictory results intermittently since.

In 2016 the current detector will be decommissioned to allow construction of a bigger detector for future runs. This bigger detector, using the new calibration will push even further into WIMP parameter space, either detecting WIMPS or ruling out more models. As the limits keep getting pushed lower, we may need to re-think what might or might not constitute the dark matter that fills the universe. Even as detections appear to be made we need to proceed with caution. Experimental results are usually not actual news. It takes time for our understanding to evolve, to be recalibrated and to move us forward.

Perhaps that list helps us recall that the hard work is in sifting the haystack just a little bit better and that generation after generation of scientists might need to keep resifting. Once I heard a quote, I don’t recall where, attributed to Alfred Wegener just before he perished in a blizzard. Wegener was the meteorologist who proposed the idea of continental drift, an idea resoundingly rejected at the time by geologists. It took many decades before it became a theory routinely taught to school children.

The quote as I recall it: “Science is a social process. It happens on a timescale longer than a human lifetime. If I die, someone takes my place. If you die, someone takes your place. What matters is getting it done.”

We can’t worry about time slipping into the future. All the time that has slipped into the past can be overwhelming when we look at the short time we have to solve whatever problem is holding our interest at the moment. All we can do is take another crack at the haystack in front of us.