Enlarge / Scientists with Italy’s DAMA/LIBRA collaboration have been claiming to see a seasonal shift in “dark matter wind” for over 20 years. New results don’t support that, and a new hypothesis might explain what the collaboration is really seeing. (credit: X-ray: NASA/CXO/Fabian et al.; Radio: Gendron-Marsolais et al./NRAO/AUI/NSF Optical: NASA/SDSS)
Over 20 years ago, a team running an underground experiment in Italy announced that it had detected evidence of dark matter—a claim the collaboration maintains to this day. But many physicists remain unconvinced that the signals detected were really due to dark matter, and outside experimental results have been mixed.
A new paper in Nature reporting on results of a different, complementary experiment found nothing to support the controversial claim. And a draft paper posted to the online arXiv proposes an alternative hypothesis for what the Italian collaboration might really be seeing in their data. But neither paper is sufficient to put the matter to rest once and for all.
Seeing the dark
Dark matter is a mysterious substance that physicists believe comprises around 27 percent of the Universe. (The ordinary matter we see everyday accounts for just four percent, with the remaining 69 percent due to the even more mysterious dark energy.) The most likely candidate for the source of dark matter is a class of particles known as weakly interacting massive particles (WIMPs), named because they rarely interact with ordinary matter.