Photomultipliers of the LUX detector

Photomultipliers of the LUX detector

By Olivia Zhu

How far would people go to detect something that, by definition, isn’t there?

Scientists from the Large Underground Xenon (LUX) experiment have built a facility a mile underneath the black hills of South Dakota in hopes of finding evidence of dark matter. Dark matter currently “does not exist” because it cannot be detected with light; however, it must be there, as it exerts a gravitational force on “normal” matter. Actually, it should have a rather large presence: the universe is made of 4.9% normal matter, 26.8% dark matter, and 68.3% dark energy.

On Jan. 16, Carmen Carmona-Benitez, a LUX representative from Case Western Reserve University in Cleveland, presented LUX’s latest findings to Duke’s Physics Department. The LUX experiment hopes to detect the presence of weakly interacting massive particles (WIMPs), a candidate component of dark matter. Carmona-Benitez described their detector, which has photomultipliers at either end; these photomultipliers will sense light emitted from electrons when WIMPs collide with their nuclei.

The LUX experiment, comprising 100 people, is a collaboration of 17 institutions in the United States and a few internationally. How could 100 extremely talented scientists work together without butting heads? Well, Carmona-Benitez stressed that many of the scientists design the machinery supporting the primary WIMP detector. For example, the team at University of California Santa Barbara built a filter system for the enormous tank of water that shields the detector from external gamma radiation. Another team contributed four thermosyphons used to cool the detector.

Thanks to these various efforts, LUX has achieved unprecedented sensitivity to WIMPs; however, no WIMP has been detected. This suggests that WIMPs, in fact, do not exist, and therefore do not comprise dark matter. The LUX team, though, refuses to give up and is creating a new and improved LZ experiment for WIMP detection.

The Triangle Universities Nuclear Laboratory (TUNL), based at Duke, is also trying to understand dark matter by studying neutrinos.