Physicists Create Heaviest Antimatter Nucleus Yet

KATHLEEN DAVIS: This is Science Friday. I’m Kathleen Davis.

CHARLES BERGQUIST: And I’m Charles Bergquist. If you ever happen to need a gram of antimatter. NASA estimates it’ll cost you about $62.5 trillion. Making antimatter is expensive and controlling it, holding it, manipulating it– that’s even more so. So why bother? It all comes down to one of the most fundamental questions about the universe. Why is there something rather than nothing? Why do we have stuff?

Antimatter is just like matter, except for one thing. Antimatter particles have the same mass as ordinary matter but an opposite charge. Each particle has its own anti counterpart. For example, an electron has a negative charge. So an antielectron, called a positron, weighs the same but has a positive charge. But beyond that simple definition, what exactly is antimatter? How do you make it? And why do we care?

Joining me now is Dr. Jamie Dunlop. He’s the associate department chair for nuclear physics at Brookhaven National Lab on Long Island. An experiment there recently created the heaviest exotic antimatter nucleus to date, something called antihyperhydrogen-4. Welcome to Science Friday, Dr. Dunlop.

JAMIE DUNLOP: It’s a pleasure to talk to you.

CHARLES BERGQUIST: You as well. So to start, what is antihyperhydrogen-4? That’s a mouthful.

JAMIE DUNLOP: Yeah, let’s break it down. So there’s the “anti” piece, which means that it’s made completely out of antimatter. There’s the “hyper” piece, which I’ll get into in a bit. The “hydrogen-4” means that it’s made out of four different nucleons. It’s basically like helium. So you’ve got a proton, you’ve got a– two neutrons, and then you’ve got a heavier counterpart of the proton, which is a lambda, and that’s the hyper part. In any case, it’s the heaviest piece of antimatter that we’ve ever been able to make and observe in the lab. And by doing that, we’re trying to understand its properties relative to its partner matter, the hyperhydrogen-4 nucleus.

CHARLES BERGQUIST: So I could think of it as like an antihelium, but with a little bit extra– like you’ve supersized the antihelium.

JAMIE DUNLOP: Absolutely. Yeah, we’ve made its mass just slightly higher and so that makes it actually a lot easier to detect.

CHARLES BERGQUIST: So your collider, RHIC, is basically slamming gold ions together at incredible speeds. How do you get from that to making antimatter?

JAMIE DUNLOP: That’s a that’s a very good question. So antimatter and matter are created when you convert pure energy into mass. E equals mc squared found back in 1905 by Einstein. So when we take these nuclei that are very high energies and we slam them together, you create a little region of matter that’s maybe 2 trillion degrees Kelvin or Celsius, it’s the same thing at that temperature, and that lasts for something like 20 yoctoseconds, 30 yoctoseconds– one of my favorite units– very small pieces of matter, very short amount of time at a very high temperature. And so in that you’ve created thousands of particles that are all moving around and some of them find each other. So you’ve created thousands of antimatter particles. And every now and then they’re going to find a partner, or they’re going to find two partners, or they’re going to find three partners and they’re going to make this chunk of antimatter– these nuclei that are made out of antimatter, these chunks of antimatter.

CHARLES BERGQUIST: So it’s not like you woke up one morning and said, I’m going to make antihyperhydrogen-4. You said, I’m going to do this collision and the conditions were just right to find it in the soup of other stuff.

JAMIE DUNLOP: Absolutely. And, in fact, this is this is one piece of the physics that we do at the Relativistic Heavy Ion Collider. There’s a whole other set of physics that we do is trying to understand the properties of the matter that we create at these high temperatures. But, yes– so what we did is we actually searched through 7 billion collisions, each of which creates 1,000 particles, so that’s 7 trillion particles. And we found 16 of these antihyperhydrogen-4. So that’s like– if you think about orders of magnitude, that’s like an expensive lunch versus the entire size of the United States federal budget. So it’s looking at a very small needle in a very large haystack.

CHARLES BERGQUIST: Very large. So you mentioned the properties of this stuff. Does it actually act just like other matter in every way except the charge and spin, I mentioned? I’m thinking of things like magnetic fields, electric charges, gravity, all those good things.

JAMIE DUNLOP: Yeah, no, that’s a very good question. We think it does. Theoretically, it should have the same mass. It should interact with gravity the same way. Electromagnetically, it’s just got opposite charge. But other than that, it interacts with electromagnetism the same way. There are all different types of forces.

However– again, the mystery is why the universe that we see, that is us, the trees, the sky– why that’s all matter? Now, at the beginning, in the Big Bang, there was lots of antimatter, there was lots of matter around, and the matter found its antimatter partners and they all annihilated. And– but there was just a little bit left over, which created the matter universe that we see now, 1 in 1,000,000,000. That’s about the level.

CHARLES BERGQUIST: Do we think that there was just a little bit extra matter created or was is the antimatter that was created somewhere else, there’s a pool of it somewhere in deep space?

JAMIE DUNLOP: Yeah, no, we don’t see any evidence of it being somewhere– a pool of it somewhere in deep space. It just wasn’t created. And it’s potentially that– that’s because it’s either an accident or it’s because the properties of antimatter and matter are somewhat different. Those are the two possibilities. And so we’re looking– as scientists, we don’t really like thinking about accidents. So we’re looking to see if there are differences between the matter and the antimatter.

CHARLES BERGQUIST: So we’ve been talking about antimatter like it’s some exotic thing, but things like positrons are made all the time. You’re– even your body is emitting positrons. So why are other kinds of antimatter things so challenging to make and work with?

JAMIE DUNLOP: It’s just the energy scales you’re looking at. It’s not that challenging. I mean, right now, a mile away from me at the at the collider, we’re creating millions of particles of antimatter every second. It’s just trying to trying to find various combinations of this antimatter, various configurations of this antimatter that are rare.

CHARLES BERGQUIST: So how do you hold it, or measure it, work with it? What kind of tools do you need beyond this massive collider just creating it?

JAMIE DUNLOP: Well– OK, so we’ve got these particle detectors. So when you collide, it happens at a very small scale and it only lasts for a very short amount of time. And then the particles all stream out and they come out to something that’s our size, our scale. And we have these detector complexes that are about the size of a house that look at various properties of these particles that come out– their speed, their momentum, their energy, what their angles are, their various correlations. And these are the things that we use to trace back the properties that happened at the at the collision and also to understand the properties– how we identify the actual antimatter nuclei.

CHARLES BERGQUIST: So have scientists seen the anti versions of all of the different particles yet?

JAMIE DUNLOP: Most. But, again, we when you get to the nuclei level, when you get to the nuclear level, we’ve only gotten up to a nuclear number four or so. We haven’t gotten up– we haven’t made anti-lead, we haven’t made anti-gold. We’ve seen anti of everything else. There are some questions is on the neutrino– in the neutrino area, where there’s some missing piece in terms of the spin of the neutrinos versus the spin of the antineutrinos. We only see one type of spin of the neutrinos and the opposite type of spin at the antineutrino. So there are some theories and some tests that we’re doing in experiments that maybe the neutrino is its own antiparticle. So it’s not even a reasonable question to ask whether you’ve seen an antineutrino.

CHARLES BERGQUIST: Is there an antinucleus that you would really want to create or is it just like heavier is always going to be better for you?

JAMIE DUNLOP: I think heavier is always going to be better. I mean, it would be nice to get up to the lithium level because what we say is that at our colliders we create little bangs. And so we want to make as much of an analogy to the Big Bang as we can. And the Big Bang nucleosynthesis, the thing which tells you about the properties of the Big Bang by the nuclei that are created in the big bang– that basically goes up to lithium and doesn’t get much higher. So if we could get to lithium, then we could say that really we are doing little bang nucleosynthesis. But that’s probably not going to happen with the within the technology that we can create on earth probably for the next 1,000 years.

CHARLES BERGQUIST: So, I mean, what would it take to theoretically do something like that? Is it something that makes more antiparticles or something that does better at squishing them into the right neighborhoods so that they can connect? Or what is it?

JAMIE DUNLOP: Yeah, something that makes more antiparticles. You would have to bring up the energy, bring up the temperature of the of the collisions and also create many more per second than we can do with our current technology. It’s orders of magnitude, probably three orders of magnitude or four.

CHARLES BERGQUIST: So about 14 years ago, we had a segment about some researchers at CERN who had trapped antimatter for the longest time to date. They said it was a time that you could measure with a watch. And Ira asked these guys, what practical use does this research have? And the guest’s answer was absolutely none. Are we any closer now to having practical applications of this antimatter research?

JAMIE DUNLOP: Well, I don’t know about the antimatter itself, but the research has huge numbers of spinoffs. So the precision that we can control these beams, the accelerator technology can be used for many other things. For example, here at Brookhaven, we use the same accelerator complex to make isotopes for medical uses, things that are used to cure cancer. We use the same accelerator complex to do studies of radiation in space.

There’s a NASA space radiation laboratory that looks at the effects on biological systems and electronic systems for space travel. You mentioned positrons that are in our body. There’s the PET scanning, Positron Emission Tomography, which uses the very specific properties of matter/antimatter annihilation to do precision scans of the human body. So there are lots of spinoffs from the technology we want to use for fundamental research that then are useful for other things to society.

CHARLES BERGQUIST: I mean, these spinoffs are definitely important, but is there a reason that you tell people that they should care about antimatter?

JAMIE DUNLOP: Well, I mean, from a fundamental standpoint, we’re here, right, that the universe is matter, not antimatter is a fundamental mystery. There are many places where we’re investigating why that could be the case. This is just one of them.

CHARLES BERGQUIST: I guess being here is a good reason to care.

JAMIE DUNLOP: Yeah.

CHARLES BERGQUIST: Dr. Dunlop, thanks so much for joining us.

JAMIE DUNLOP: Thank you.

CHARLES BERGQUIST: Dr. Jamie Dunlop is the associate department chair for nuclear physics at the Brookhaven National Laboratory on Long Island in New York.

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