There is overwhelming evidence that dark matter makes up most of the matter in the Universe—researchers have even mapped its distribution on cosmic scales by observing how it stretches the images of distant galaxies. But we still don’t know what dark matter is. This unresolved puzzle is being tackled by direct-detection experiments that continue to break record after record with their sensitivities to feeble particle interactions. Today two leading dark matter searches—the XENON experiment under the Gran Sasso massif in Italy and the PandaX experiment at the China Jinping Underground Laboratory, the world’s deepest laboratory—publish analyses of their latest runs.
Reporting what Big Think called one of the best “null result” in history, XENON shows that a tantalizing signal reported in 2020 was due to background noise rather than to new physics and sets stringent limits on various dark matter types that had been invoked to explain such a signal . The PandaX Collaboration performed a similar measurement, also detecting no events over the expected background . The collaboration used its null result to derive the tightest constraints to date on properties of a type of dark matter called light fermionic dark matter.