Researchers Trap Antimatter For Record 16 Minutes

June 10, 2011

NPR Staff

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IRA FLATOW, host: This is SCIENCE FRIDAY, I'm Ira Flatow, trying to overcome a bout of laryngitis so see if you can hang in there with me for this program. Our current ideas of the universe say that when the universe was created in the Big Bang, billions of years ago, not only was matter created but so was matter's mirror image, antimatter.

One of the great mysteries about the universe is where did all the antimatter go. How come we don't see it anymore? And if you want to see it to study it, we have to create it in the laboratory, but when we do, it only lasts - oh, exists for a fraction of a second, until now.

Last November, researchers created and trapped anti-hydrogen, the simplest atom of antimatter, holding it in a magnetized bottle for only a fraction of a second. Now that same team is back, and they've raised the bar, trapping antimatter for longer than ever before, this anti-hydrogen around 16 minutes, just about as long as they wanted.

So now, what do you do with it? Here to answer that question is Dr. Jeffrey Hangst. He's professor of physics at Aarhus University in Denmark. He's also the leader of the Alpha Collaboration at CERN in Geneva. Welcome back, Dr. Hangst.

Dr. JEFFREY HANGST: Thank you, Ira, it's good to be back. I must be doing something right.

FLATOW: Well, what you've done is you've trapped antimatter for longer, for, what, 16 minutes?

HANGST: Yeah, 1,000 seconds is 16 minutes, give or take.

FLATOW: And could you have gone as long as you wanted to?

HANGST: Well, we don't really know the limit yet. This was as long as we conducted the experiment and could get statistics enough to see the signal. This takes some time, of course, and we've seen some events at longer time, but we can't say 100 percent certain that they're above the background. So 1,000 seconds is firmly established, and we can continue to look for longer, but it's not our highest priority right now.

FLATOW: Talk about anti-hydrogen. How is it different than regular hydrogen?

HANGST: Well, that's what we'd like to know. We'd like to measure the characteristics of anti-hydrogen and see if it's the same as hydrogen. The fundamental difference is, of course, that anti-hydrogen is made of anti-particles. So instead of a positive proton, you have a negative anti-proton. Instead of an electron in hydrogen, you have a positron, an anti-electron.

So that's the structure of the thing. The question is whether this thing obeys the same laws of physics as normal hydrogen, and that's what we're finally getting ready to measure.

FLATOW: Well, the fact that you were able to trap it in a magnetized bottle, wouldn't that tell you something?

HANGST: Well, the fact that we can trap it doesn't tell us too much yet. We need to take the next step, which is to shine light on it, both literally and figuratively. We'd like to interact with it, with its internal structure, to see what kind of color of light does it like to absorb, or what frequency of microwaves, for example, because we know those things very well for hydrogen.

So the next thing, and the thing that many of us have been working for for a long time is to measure something about this thing.

FLATOW: Do the anti-particles conform to the other - for lack of better phraseology, -laws of nature like the regular particles, like gravitation, magnetism, things like that?

HANGST: We know absolutely nothing about gravitation in antimatter, as far as measurements are concerned. In fact, that's one of the exciting things about this new development is that having them around for a while may allow us to do what we need to do to them to study their gravitational influence in the Earth's gravitational field.

It's a very special experiment. Antimatter in a matter gravitational field, we've never tried that before. It's an extremely difficult experiment. But more fundamentally - OK, we know that the anti-proton has a charge that's very close to the proton and that the positron has a charge that's very close to that of the electron in magnitude. They're opposite, of course.

But we haven't been able to study a composite antimatter system like this with any kind of real precision, and that's what we'd like to do because hydrogen is something we really understand very well in physics. So if we can do the same sort of things with anti-hydrogen, we can compare them.

FLATOW: And it's the most abundant element in the universe.

HANGST: Hydrogen is, yes, and anti-hydrogen is the least abundant element in the universe.

FLATOW: So where does it all go?

HANGST: That's the question. You know, in physics, we like to think big. The paleontologists are missing a few dinosaurs and fossils along the way. We've misplaced half the universe. And we really don't know what happened to it. So as you pointed out, the Big Bang Theory says that there should have been equal amounts of matter and antimatter at the beginning of the universe. And for some reason, only the matter survived.

Of course, they can't be in the same place at the same time. We can't have both. But why couldn't we have an antimatter universe? That - as far as we understand today, that should have been equally probable. So we just don't know why nature chose one and not the other.

FLATOW: And the first thing you'll be doing, then, is - now that you've trapped you in the bottle, you say you would shine some laser light on it.

HANGST: The first thing we'll actually do is microwaves. You think of these little atoms as magnets. They're trapped because they have a little magnetic moment, as we call it. They're like a small bar magnet. And that's trapped in this magnetic field. If you shine some microwaves of the right frequency on that atom, you can turn its magnet the other direction, and then it'll fall out of this trap and annihilate, and we can see that. Even just a single atom, if it comes out, we can detect it. So there, antimatter gives you kind of a detection bonus. It's easier to detect than matter when it annihilates.

So that's what we'll do. We'll shine some microwaves on it and see if it likes the same frequencies that hydrogen would like. That would be the first test of this sort of symmetry between hydrogen and anti-hydrogen. It's not the most precise one, but it's a first step.

FLATOW: Some questions coming in from our listeners. Here's on our SCIENCE FRIDAY Facebook page. Daniel Yout(ph) would like to know about whether the anti-hydrogen could be the start of a new periodic table.

HANGST: Well, that's an excellent question. In fact, it's a timely question because very recently, in Brookhaven National Laboratory at the RHIC accelerator, a group created anti-helium nuclei in collisions of very heavy ions. But that's very, very difficult, and they don't produce them in a way that you could catch them. They just demonstrated that anti-helium nuclei - that's number two on the anti-periodic table - that they exist.

But there's really no chance of doing what we do to make an anti-helium atom. So these things just existed a little bit in a collision and then ran into some material. So it's very, very, very unlikely, I would say impossible, to make anti-helium atoms and try to study them.

FLATOW: But you could make a new periodic table. We make these little, you know, high-level particles that last for a fraction of a second. Wouldn't you...

HANGST: Yeah, that's right. We believe that there is an anti-periodic table, right, that you could have an anti-universe full of anti-elements. But it's very difficult for us to go and do atomic physics on those. So you can demonstrate so far that we've got two of them.

FLATOW: And how difficult is it to go up then and create new elements, anti-elements?

HANGST: We say, in the Brookhaven paper, it takes about a factor of 1,000 every time you want to add one mass. So going from hydrogen to deuterium, right, that's a proton and a neutron, it - you'll get 1,000 times less deuterons for the same type of interaction.

So that's a thousand for every one. So you can see it gets really, really unlikely very quickly to get anything heavier. So I think you can just forget that and hope that we can find something with anti-hydrogen.

FLATOW: Let's go to the phones. David(ph) in St. Louis, hi, welcome.

DAVID: Hi, thank you. I was wondering - you talk about the annihilation, when the matter meets the antimatter, and I was reading about it this week. And I was wondering, does this interaction obey the laws that we think of like the conservation of mass and energy? Like in a nuclear reaction, you'll lose mass, but you'll gain energy. What happens when these two - what exactly do you mean by annihilation? Thanks.

HANGST: Yeah, that's a good question. What happens exactly is that the quarks in the anti-proton annihilate with quarks in a nucleus in the material, and that produces energy for just a very fleeting moment, and what happens in practice is that energy quickly becomes mass again. So that's Einstein, E=MC2. This energy that goes into the annihilation quickly generates new mass. And this mass is in the form of subatomic particles we call pions.

And they come screaming out of our apparatus, and we can measure them. So as far as we know, these annihilation events obey conservation of mass and energy, and no one's ever seen any kind of deviation from that. But the energy quickly becomes mass that flies out and we can measure.

FLATOW: Now that you've proven you can hold on to these particles long enough to get a good look at them, after you do your microwave experiment, what's the next - is there a better detector you're working on?

HANGST: No, there's a - the next thing, you want to keep making more and more precise measurements, right. The thing about atomic physics is atomic physicists are the guys who really know how to measure things precisely. So for example, the energy of the one to two transition, we call it in hydrogen, from the ground state to the first excited state, is known to one part in 10 to the 14, approximately.

All right, that's point-zero, 14 zeroes, one in precision. So in order to do the best test, you'd like to repeat that experiment in anti-hydrogen, and that requires lasers, a very special laser system. So starting next year, we hope, we'll be able to shine lasers on the anti-hydrogen that's in the trap and start seeing that it wants exactly the same color as hydrogen. That's figuratively color because the light that we're going to use is invisible.

FLATOW: And one last question, in about a minute that we have left. I'll see as many questions as I can get in. How do you make antimatter?

HANGST: Well, this - again, it's all up to Einstein. CERN uses energy from a particle accelerator to create new things. Right, that's what they're looking for. When they're searching for the Higgs boson, they're using a very high-energy particle accelerator to create some new mass, E=MC2. You have to do the same thing to make an anti-proton.

We use energy at a particle accelerator, to lower energy than the LHC, but we need the energy to create the mass in the anti-proton, and of course we create proton-anti-proton pairs. That's what the law tells us. But they're made in the accelerator, and that's why we have to be at CERN to make the anti-protons.

It turns out you can buy positrons. You can get a radioactive source that's made, in this case, in South Africa that just sits and emits positrons all day long. And then we have a device that accumulates them and stores them up.

FLATOW: Quite interesting. I wish you good luck in your experiment.

HANGST: Thank you. I hope to be back soon.

FLATOW: Yeah, tell us when you do that gravity-laser experiment or getting close to it. Thank you for coming on the program.

HANGST: Thank you, Ira.

FLATOW: You're welcome, Dr. Jeffrey Hangst, professor of physics at Aarhus University in Denmark.

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FLATOW: We're going to take a break, and when we come back, we're going to talk about autism and all kinds of new research about it. So stay with us. We'll be right back after this break.

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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