This radio about dark matter could fit into the new physics

Physicists from Stanford University and SLAC they have built a device that they hope to detect dark matter, although it is true which theoretical particles they think they will find – hidden photons or small spots called axions – are still in question.

Hidden photons are thought to be very similar to regular photons, known as light particles, except that they have mass and interact much weaker with ordinary matter, hence their secrecy. Axions are a type of subatomic particle (more precisely a boson) whose existence, if proven, could solve a long-standing problem with the way physicists understand the universe.

Dark matter certainly seems to exist, because its gravitational effects can be seen in almost all galaxies. But while dark matter can be viewed indirectly, whatever actually makes it, partially or completely, has never been discovered.

Prototype dark matter detector.

DM Radio Pathfinder, without its cylindrical niobium.
Photography: Isaac Schultz

The culprit for dark matter is not just one thing; There may be several reasons why Fr. 27% of the universe it seems to be dark matter. Popular candidates include low-interaction mass particles (WIMP) and much less massive axioms, hidden (sometimes called dark) photons, and a class of objects known as massive compact halo facilities (MACHOs). WIMPs used to be previous candidates for dark matter, but a number of elaborate experiments set up to detect them showed “a lot of nothing,” as Gizmodo reported in 2020

“Axion is always hard to explain, but there are several reasons why physicists are generally so excited about it,” Peter Graham, a theoretical physicist at Stanford University, told Gizmodo. but then he realized that it would actually be a good candidate for dark matter. “

It was named after the laundry detergent, axions are not described in the Standard Model of Particle Physics, but would explain a frustrating problem in this area: that some predicted neutron characteristics do not occur in nature. (Physicists are, as you might expect, big fans of Occam’s razor: the idea that the simplest solution is probably right – there’s no need to complicate things too much.) they find.


DM Radio Pathfinder, which hunts for hidden photons.
Photography: Isaac Schultz

“It’s the only really strong way to solve this problem with a standard model,” said Kent Irwin, a physicist at Stanford University and SLAC. and Dark Matter radio chief researcher, he told Gizmodo. “Dark matter aside, if the axion doesn’t exist, it would cause real headaches for the Standard Model.”

The Dark Matter Radio project tries to detect hidden photons in a certain frequency range by methodically turning the dial, which means to the patient, by a comprehensive search of wavelengths where such a particle could sound. Later generations of radios will chase axioms.

As for subatomic particles, some are very small, while others are extremely small. Some are massive enough to be detected with relative ease as they break down other matter, such as collisions that occur in particle collisions. Other particles behave so elusively that they are easier to detect as waves, due to how diffuse they are in space.

“[An axion] is so light that quantum mechanics tells you that it actually has to be spread over a very long distance, ”Graham said. “You can think of it more as a background wave, a background fluid you’re somehow immersed in.”

If dark matter is at least partially axions or hidden photons, then that matter flows through you and me in piles every second. I like neutrinos, theorized particles are both ubiquitous in ordinary matter because of their abundance and practically transcendent because of how little they interact with it. Scattered as they are supposed to be, axion waves can be as wide as a few feet to football fields.

That is why Radio Dark Matter searches for particles of dark matter by looking for their background or a certain frequency on which they travel, just as a given radio wave can only be caught on the frequency on which it broadcasts. This particular radio needs to be protected from any other type of wave, so it is dipped in dewar helium cooled to just above absolute zero. (Dewar is basically a vacuum bottle — and in this case a barrel — for keeping the material at a certain temperature, in this case to keep the helium very cold.)

The current Dark Matter Radio experiment is a prototype, or Pathfinder, for the larger projects below. It consists of a liter cylinder made of superconducting metal niobium, around which niobium wire is tightly wound. It kind of looks like someone wound the guitar string on the vertical axis of the spool instead of its horizontal axis. This is the Pathfinder inductor. If a hidden photon that resonates at the frequency to which the Pathfinder was tuned passed through it, a change in the magnetic field would cause voltage around the inductor of the invention.

DM Radio device physicist.

Equipment on which the DM Radio Pathfinder is mounted when immersed in helium.
Photography: Isaac Schultz

“The null hypothesis is that there should be no radio waves inside that box unless, in this case, there are hidden photons, which are our special taste of dark matter,” said Stephen Kuenstner, a physicist at Stanford University and a member of the DM Radio team. Hidden photons “can pass through a box and have a certain probability of interacting with a circle in the same way that a wave would work,” Kuenstner said.

To amplify any signal that the Pathfinder captures, there is a hexagonal shield of niobium plates that coats the above components and acts as a capacitor. This amplified signal is then transmitted to a quantum sensor called SQUID (superconducting quantum interference device), a technology invented by Ford Motor Company in the 1960s. SQUID lives at the bottom of the radio and measures and records all received signals.

The lower the expected mass for the axion, the more elusive the particle is, because its interactions with ordinary matter are in proportion to its mass. That is why it is important that the next generation of DM radios become more sensitive. The way the experiment was set up, “the frequency on the dial is the mass of the axion,” Irwin said. Nice! The mass of these particles cannot be compared to the smallest things you can think of, such as atoms or quarks. These particles would be somewhere between a trillionth and a millionth of an electron volt, and the electron volt is about a billionth of the mass of a proton.

Pathfinder’s room is comfortable and looks a lot like an ordinary physics lab, except for the threatening-looking equipment that immerses Pathfinder in helium and large helium gas tanks that are attached to the wall in the event of an earthquake. In 1989, Irwin was a graduate student at Stanford, working in a university basement when a 6.9-magnitude earthquake shook the area, knocking fire extinguishers off walls. It is safe to say that the laboratory does not take risks with helium (although it is not flammable, the gas can expel oxygen, causing suffocation).

The helium used by Pathfinder is gaseous and remains relatively warm at 4 kelvins (in other words, four degrees above absolute zero), but the next experiment – Dark Matter Radio 50L – will use liquid helium, cooled to less than one degree above absolute zero. All the better for listening to dark matter.

The DM Radio 50L is located in the corner of a large room in the Hansen Experimental Physics Laboratory at Stanford. The room looks a bit like a TV room in Willy Wonka’s factory; it has high ceilings, a lot of unfathomable equipment and is bright white. Two 6-foot-high dilution coolers on one side, leaning against a deep closet, are radio. The two machines are powered by helium gas located in tanks in the next room, which are then cooled to liquid helium from cold 2 kelvins. The magnets inside the gilded copper and aluminum casings will do the job of converting all detected axioms into radio waves that physicists will interpret.

“The community of particle physics is – an analogy is often said – just like a warship. It takes some time to turn around and there is a lot of momentum, ”Irwin said. “While I think there’s a lot of reason to believe that these radio-like dark matter signals are more attractive – action signals – than WIMP, there are still a lot of giant experiments looking for little things, which is good.”

Horizontal dilution cooler in the basement of Stanford University.

Horizontal dilution cooler, part of the DM Radio-50L experiment.
Photography: Isaac Schultz

Other experiments in axion hunting include ADMX experiment at the University of Washington, QISMET experiment in Fermilab, ABRACADABRA experiment at MIT and HAYSTAC search at Yale. DM Radio is similar to several of these, but seeks axioms in the second range. Together, the set of axion hunts across the United States and beyond limits the possible masses of axions.

Radio Dark Matter Radio should be considered more of a family of experiments: the team is currently working with the Ministry of Energy on a next-generation experiment that will look for axioms in cubic meters, hence its name DM Radio-m³. In the distant future, Irwin and his team have aspirations for a project called DM Radio-GUT, which would be closer to the scale of some of the largest physical experiments on the planet.

Taken together, the experiments clean a huge range of the most promising range for axial mass. All in all, Irwin said, a favorite area for axion mass could be explored over the next few decades using larger experiments – although the team could simply find axion before that, potentially ending the hunt for dark matter altogether. With enough listening, we could have a whole new particle for textbooks. Or maybe there will be radio silence.

More: The main suspect in dark matter may be fleeing neutron stars

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Naveen Kumar

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