Latest news with #WIMPs
Gizmodo
08-07-2025
- Science
- Gizmodo
Record-Setting Dark Matter Detector Comes Up Empty—and That's Good News
WIMPs (weakly interacting massive particles) are one of the most serious contenders for dark matter—the 'missing' mass supposedly constituting 85% of our universe. Given its elusiveness, dark matter tests the patience and creativity of physicists. But the latest results from LUX-ZEPLIN (LZ), the South Dakota-based detector, may have brought scientists a small step closer to catching WIMPs in action. In a recent Physical Review Letters paper, scientists analyzed 280 days' worth of data from LUX-ZEPLIN, reporting the tightest ever upper limit on WIMPs. The result—a near fivefold improvement—demonstrates how physicists are increasingly getting better at circumventing the problem that dark matter is, well, dark; the elusive stuff evades any detection method that depends on materials interacting with visible light or other types of radiation. There's ample evidence to suggest that dark matter does in fact exist, including numerous astrophysical observations hinting at some invisible matter exerting gravitational force on objects we can see. Physicists, as a result, tend to use materials that we can see, such as liquid forms of heavyweight elements like xenon, and simply wait for some unknown particle to interact with it. That strategy—waiting for particles to interact with heavy elements—is a well-tested approach for detecting WIMPs, hypothetical particles that interact with gravity but on a scale so tiny that only the most sensitive detectors might catch a glimpse. The LUX-ZEPLIN experiment, located one mile underground in a decommissioned South Dakota gold mine, employs nearly 15,000 pounds (7 tons) of liquid xenon. The chemical element's high atomic mass and density make it potentially easier for scientists to detect any unknown particles that may pass through the detector. Also, liquid xenon is transparent, preventing any unwanted noise—usually arising from radioactive matter around the detector—from spoiling an experiment. 'If you think of the search for dark matter like looking for buried treasure, we've dug almost five times deeper than anyone else has in the past,' said Scott Kravitz, a physicist at the University of Texas at Austin and deputy coordinator for LZ, in a press release. 'That's something you don't do with a million shovels—you do it by inventing a new tool.' The latest experiment also represents the first time the LZ team applied a technique called 'salting,' in which false WIMP signals were added in advance. This helped the researchers—who, of course, would love to find dark matter—avoid bias and stay skeptical of potentially promising signals. 'There's a human tendency to want to see patterns in data, so it's really important when you enter this new regime that no bias wanders in,' said Scott Haselschwart, a physicist at the University of Michigan and LZ physics coordinator, in the same release. 'If you make a discovery, you want to get it right.' The next steps for the LZ experiment are to continue pressing against the upper limit for WIMPs and utilize the detector's cutting-edge technology to probe other interesting and rare physics processes, explained Amy Cottle, a physicist at University College London also involved with LZ, in the statement. 'We've demonstrated how strong we are as a WIMP search machine, and we're going to keep running and getting even better—but there's lots of other things we can do with this detector,' she said.
Hans India
24-06-2025
- Science
- Hans India
Dark Matter: The cosmic puzzle that still evades discovery
In 1933, Swiss astrophysicist Fritz Zwicky made a groundbreaking observation while studying the Coma Cluster, a collection of galaxies over 300 million light-years away. He noticed the galaxies were spinning far too quickly to be held together by the visible matter alone. The only explanation? There had to be unseen mass providing the extra gravitational pull. He called it 'dunkle Materie' — dark matter. Nearly 100 years later, dark matter remains one of the greatest mysteries in science. It makes up around 27% of the universe, yet no one has ever seen it. It doesn't emit, reflect, or absorb light, making it completely invisible to telescopes. But without its gravitational influence, galaxies would fall apart, and the structure of the universe itself wouldn't exist. The Gravity We Can't See Evidence for dark matter is overwhelming. Stars on the edges of spiral galaxies rotate at speeds far too fast for visible matter alone to account for. Galaxy clusters move as though they're wrapped in vast, invisible halos. Even the early universe's structure — from galaxies to vast filaments of cosmic webbing — appears to have been shaped by something unseen holding it all together. At one point, scientists suspected neutrinos might be the answer. These ghost-like particles are abundant and barely interact with matter. But they're too light and too fast-moving to form the kind of gravitational scaffolding needed. Where Are the Particles? Physicists turned to more exotic candidates. One popular theory was WIMPs — Weakly Interacting Massive Particles. These theoretical particles could have mass and exert gravity, yet remain undetectable because they barely interact with ordinary matter. Deep underground labs were built with sensitive detectors waiting to catch a WIMP colliding with an atom. But decades have passed, and no clear signal has emerged. Supersymmetry offered another tantalizing idea — every known particle might have a heavier 'partner.' One such partner, the neutralino, seemed perfect for dark matter. Yet even after firing up the Large Hadron Collider, these hypothetical particles have never shown up. Now, physicists are widening the search. Some suspect dark matter might be made of ultra-light particles like axions, or that it resides in a hidden "dark sector" with its own rules and forces. Others are daring to rethink gravity itself — perhaps we don't need dark matter, just a new understanding of how gravity works. A Mystery That Could Rewrite Physics The stakes are massive. Cracking the dark matter code could transform our understanding of matter, forces, and the very origins of the universe. It could lead us to a new physics — one that goes beyond the Standard Model that currently explains everything from atoms to quarks. But for now, we remain in the dark. Dark matter doesn't shine, collide, or leave trails. All we know is that it's out there — shaping galaxies, pulling clusters together, and silently sculpting the universe. Until we find it, the cosmos will remain a place of wonder and unfinished questions — where the most powerful force holding everything together remains hidden in plain sight.
Yahoo
15-03-2025
- Science
- Yahoo
Scientists Find Evidence of a New Form of Dark Matter Swirling at Center of Our Galaxy
There's a new twist in the hunt for dark matter, the invisible substance believed to make up 85 percent of all the mass in the universe: it may actually be way lighter. In a study published in the journal Physical Review Letters, an international team of researchers propose a new form of the hypothetical substance that's lower in mass compared to other dark matter candidates, which could explain a mysterious phenomenon at the center of our Milky Way galaxy, in a region called the Central Molecular Zone (CMZ). "At the center of our galaxy sit huge clouds of positively charged hydrogen, a mystery to scientists for decades because normally the gas is neutral," said study co-lead author Shyam Balaji at King's College London in a statement about the work. "So, what is supplying enough energy to knock the negatively charged electrons out of them?" "The energy signatures radiating from this part of our galaxy suggest that there is a constant, roiling source of energy doing just that," Balaji added, "and our data says it might come from a much lighter form of dark matter than current models consider." While scientists have extensive evidence that dark matter exists, determining what it is and where it resides remains one of the biggest questions in physics, with theories ranging from parallel universes to primordial black holes. But one of the original and still leading explanations for dark matter is that it comprises a type of nearly undetectable particles called Weakly Interacting Massive Particles, or WIMPs. As the moniker suggests, WIMPs don't interact strongly with other particles, including light, but are massive enough that they would clump together in the way that astronomers have observed galaxies and other cosmic structures do — which dark matter, through its gravitational influence, is hypothesized to govern the shapes of from the shadows. But perhaps there's more than one form of it that's less massive than WIMPs, as the researchers suggest. The thinking goes that in the extremely dense environment of the CMZ, these lighter dark matter particles would be constantly colliding and destroying each other upon impact, and subsequently releasing energy. This is a process known as annihilation, and the energy it liberates would then ionize nearby hydrogen gas. Conversely, the researchers argue that WIMPs and other proposed dark matter particles like axions don't undergo enough annihilation to ionize hydrogen to the extent observed in the CMZ. Nor can the phenomenon be explained by cosmic rays, powerful beams of energetic particles that zip throughout the universe at nearly the speed of light. "The biggest problem this model helps solve is an excess of ionization in the CMZ," Balaji told "Cosmic rays, the usual culprits for ionizing gas, don't seem to be strong enough to explain the high levels of ionization we observe." There's still a lot of work to be done before the idea gains more steam. But if the theory holds true, Balaji says, we'd have an "entirely new way" to study dark matter rather than just its gravitational influence; now, we could observe the ionization it causes in gases. "Dark matter remains one of the biggest mysteries in physics, and this work shows that we may have been overlooking its subtle chemical effects on the cosmos," Balaji told More on space: Scientists Intrigued by Galactic Structure That's 1.4 Billion Light-Years Wide
