Not just nothing, dark matter quests close in on dire ‘neutrino fog’ Premium

LZ experiment reveals null result in search for dark matter, prompting new challenges in physics research.

On August 28, two members of an experiment at conferences in Chicago and São Paulo had an announcement to make.

They were representing about 200 of their colleagues involved in the design, building, and operation of the LUX-ZEPLIN (LZ) experiment located 1.5 km below the earth’s surface at the Sanford Underground Research Facility in South Dakota, USA. Their news: their band of scientists had placed the tightest restrictions yet on the identity of the particles that made up dark matter.

It was a null result: it didn’t say what the particle’s identity was but suggested which identities the particle couldn’t have. And it didn’t prompt disappointment from the physics community. Instead, it prompted resignation.

Experiments similar to LZ — such as XENON-nT in Italy, PandaX-4T in China, and dozens of others around the world — have been turning up empty-handed for decades now despite heroic efforts.

Dark matter is the invisible stuff making up most of the mass in the universe, responsible for giving the cosmos its current looks. Stars, gas, and planets contribute only 15% to the universe’s mass.

The simplest contender for the make-up of dark matter is a previously unknown type of particle that doesn’t interact with photons, and lives — i.e. without disintegrating, unlike most particles — for at least the age of the universe, about 14 billion years.

This raises a question: does dark matter ever touch us? More precisely, can atomic nuclei and electrons scatter dark matter particles when they come close?