Physicists Build Donut-Shaped Magnet To Find 'Ghost-Like' Dark Matter Particle (cnet.com)

An anonymous reader quotes a report from CNET: One of the central puzzles in particle physics is discovering what particle (or particles!) makes up dark matter — the form of matter that is responsible for 85 percent of the mass in the known universe. Some physicists believe searching for a hypothetical particle known as an "axion" could lead to a better understanding of dark matter and to hunt for it, a team of U.S. physicists have recently designed and tested a basketball-sized, donut-shaped apparatus that can seek it out.

It has been believed that axions may be detectable by looking at an unusual type of neutron star known as a "magnetar". These small, erupting stars create some of the most powerful magnetic fields in the universe. Because of their giant magnetic power, axions would be converted to radio waves in the presence of the magnetar -- and thus, detectable by telescopes on Earth. That strange cosmic phenomenon inspired theoretical physicists to create the impressively-named ABRACADABRA experiment (the full name is "A Broadband/Resonant Approach to Cosmic Axion Detection with an Amplifying B-field Ring Apparatus" so the theorists deserve a round of applause for that backcronym). The experiment consists of a donut (or "toroid") shaped device, dangled in a freezer just above absolute zero and fine-tuned to create its own magnetic field. If axions exist, the magnetic field in the middle of the donut could reveal them. The study has been published in the journal Physical Review Letters.

Comments

Donut shaped?

[140Mandak262Jamuna]

We were freshman in IIT, having passed JEE, head high in the clouds, top 1000 All India Rank, all the orientation speakers calling us creme-de-la-creme of India. First Chemistry 101 class. Reading ahead for the class, our study group found there are some electron orbital stuff, n orbital, p orbital etc. One of them was described to be doughnut shaped. All of us were stumped. We did not know what a doughnut was or what it would look like.

Then one from our study group found an American chemistry text book with pictures. It spelled doughnut as donut, but had a picture. We exclaimed, "It is a damned torus! Why wouldn't they call it a torus? Why use this weird thing donut/doughnut". In the class Prof PJ Narayanan said, "... it says doughnut in the text book. Doughnut is like a vada but it is sweet not savoury, they make in the West..."

If slashdot is going to call itself "news for the nerds" the least it can do is to call that shape by its proper name, a torus.

Re:Donut shaped?

[Anonymous Coward]

Well this discussion just went pear shaped

Re: "Dark" "Matter"

[ThePyro]

Don't be so quick to dismiss dark matter! We have good reasons to speculate about the existence of a particle which doesn't normally interact with electromagnetic fields. In the example above, huge clusters of galaxies collided with each other and the ordinary matter slowed down as a result of the collision, but gravitational lensing suggests that the center of mass (i.e. dark matter) got separated during the collision. It's not a slam dunk, but it's an interesting result that suggests there's more going on than just an incomplete model of gravity.

Oblig. Bad Car Analogy

[PPH]

don't know what a torus is

Torus is made by Ford.

Physicists build donut-shaped magnet

[DontBeAMoran]

Is one of those physicists named Homer, by any chance?

Re:"Dark" "Matter"

[Sarten-X]

Since this is Slashdot, I'll throw in a car analogy, in the time-honored tradition.

You can see my car, a good distance away on level ground. It seems to be moving away from you. With more observations, you can tell it's not just moving, but actually picking up speed.

Since the ground certainly seems level, and you don't see anything else around, it's a safe assumption that my car does indeed have an engine, and someone's driving it away from you.

Now, the problem is that engine doesn't actually create any power. It just transfers the energy from its fuel, so it's also a safe assumption that my car has a fuel tank (or batteries, if electric), and that's providing the energy for the acceleration.

Now back to dark matter...

Galaxies don't have engines or fuel tanks, but we've recently confirmed that they are actually accelerating... and far more than makes sense for the amount of mass and energy we've seen. To use another car analogy, it's like having a horse-drawn cart keeping up with a race car... It's enough to suggest something really fishy is going on.

When something fishy happens in astrophysics, it means either our formulas or our models are wrong. Since our formulas seem to be correct everywhere else, we've started looking for this "dark matter" stuff, under the suspicion that it might hold the energy we're looking for... like finding rockets hidden under the bottom of the horse-drawn cart.

It is still possible that our formulas are wrong... but to match other experiments' results, they'd have to be off by an extremely small amount in some cases, and extremely large amounts in other cases. That means not just a tweak to a scalar value somewhere, but restructuring equations entirely...and we'd still need some kind of reason for the discrepancy. Draft horses don't run at race car speeds, and if they did, they wouldn't look like draft horses.

Looking for dark matter and the dark energy it caries is actually the simpler solution. The theory fits well with our existing observations, and doesn't require completely overhauling our understanding of how the universe works. If we keep running experiments like the one in TFA and finding nothing, we'll start the huge undertaking to figure out what else might be happening, but for now this is the sensible approach.