Bigger doesn’t always mean better but certain physics detectors could be the exception that confirms the rule. Especially if the goal is to detect elusive particles such as neutrinos or hypothetical particles such as dark matter. To that end, there have been some recent exciting developments.
According to observations of the universe, the stuff that we can see and interact with makes up just one-sixth of all the matter that should exist in the universe. "Dark matter", so-called because it doesn't interact with light, makes up the rest. There are many hypotheses about what dark matter actually is, but no certainties. The DARWIN and LUX-ZEPLIN collaborations, which run the biggest experiments focusing on discovering dark matter, have just announced they have united to build a new, giant next-generation detector.
The state-of-the-art xenon-based detectors currently tasked with finding such substances are the LUX-ZEPLIN and XENONnT/DARWIN experiments. Both of them will start their first science runs collecting data this year, with the hope of finally finding direct evidence that dark matter is truly out there.
Xenon is a noble gas, and in its liquid form is used as a detector as it interacts with very little things in the universe. The detectors are designed to spot flashes of light that suggest another particle hit a xenon atom and can then reveal the type of interaction that took place. The current experiments employ 7.0 and 5.9 tonnes of liquid xenon respectively.
The predecessors of these experiments were only able to reduce the range of possibilities regarding dark matter, rather than confirm evidence of it. XENON1T did spot some titillating signals but not enough to make a proper discovery. It did however observe the rarest event ever recorded, which was pretty exciting.
The next-generation multi-tonne xenon detector the DARWIN and LUX-ZEPLIN collaborations are set to design and build will be bigger and more sensitive than the current ones. And it won’t just be looking for dark matter but will also study neutrinos from the Sun and other cosmic sources.
While this new detector is currently still just an idea, another new one has begun construction. Hyper-Kamiokande, located in Japan, is a next-generation neutrino detector and from 2027 is expected to dramatically expand our understanding of the universe.
“By observing neutrinos from nuclear fusion inside the Sun, from gigantic solar flares on the Sun’s surface and from explosions of dying stars in the Milky Way and beyond, Hyper-Kamiokande will teach us about the life and death of stars,” Hyper-K collaboration member Dr Jost Migenda from King’s College London told IFLScience.
A new paper about its capabilities published in The Astrophysical Journal has astronomers excited. Despite being so well-studied, the mechanism behind core-collapse supernovas – which produce either black holes or neutron stars – is not well understood. The detector will be able to provide clearer ideas of the types of supernovas based on their neutrino signature, as long as they are within the Milky Way or thereabouts. This is unheard of.
“Up to now, we could only compare a small number of features (e.g. what the mean energy of neutrinos was; or whether there was a sudden cut-off in the event rate, which could happen if the star collapses into a black hole). That would help us narrow it down, sure; but there might still be hundreds of models matching the observed features," Dr Migenda, who is the study's main analyzer, explained.
"In this paper, we describe a method that uses the full time and energy distribution of observed neutrinos to compare them to different models. To use a metaphor: Previously, we might have been able to tell that a suspect had blonde hair and brown eyes. With this new method, we effectively get a photo of the suspect—so we have a much better chance of identifying them."
Hyper-K will also study fundamental physics and, like its predecessor, will try to look at the limits of our current understanding of the universe.