Measuring the magnetism of antimatter: Researchers measure antiprotons more accurately than ever before

Mar 25, 2013

In a breakthrough that could one day yield important clues about the nature of matter itself, a team of Harvard scientists have succeeding in measuring the magnetic charge of single particles of matter and antimatter more accurately than ever before.

As described in a March 25 paper in Physical Review Letters, the ATRAP team, led by Gerald Gabrielse, the George Vasmer Leverett Professor of Physics, and including post-doctoral fellows Stephan Ettenauer and Eric Tardiff and graduate students Jack DiSciacca, Mason Marshall, Kathryn Marable and Rita Kalra was able to capture individual protons and in a "trap" created by electric and magnetic fields. By precisely measuring the oscillations of each particle, the team was able to measure the magnetism of a proton more than 1,000 times more accurately than an antiproton had been measured before. Similar tests with antiprotons produced a 680-fold increase in accuracy in the size of the magnet in an antiproton.

"That is a spectacular jump in precision for any fundamental quality," Gabrielse said, of the antiproton measurements. "That's a leap that we don't often see in physics, at least not in a single step."

Such measurements, Gabrielse said, could one day help scientists answer a question that seems more suited for the philosophy classroom than the physics lab – why are we here?

"One of the great mysteries in physics is why our universe is made of ," he said. "According to our theories, the same amount of matter and antimatter was produced during the Big Bang. When matter and antimatter meet, they are annihilated. As the universe cools down, the big mystery is: Why didn't all the matter find the antimatter and annihilate all of both? There's a lot of matter and no antimatter left, and we don't know why."

Making of protons and antiprotons, Gabrielse explained, could begin to answer those questions by potentially shedding new light on whether the CPT (Charge conjugation, Parity transformation, Time reversal) theorem is correct. An outgrowth of the of particle physics, CPT states that the protons and antiprotons should be virtually identical – with the same magnitude of charge and mass – yet should have opposite charges.

Though earlier experiments, which measured the charge-to-mass ratio of protons and antiprotons, verified the predictions of CPT, Gabrielse said further investigation is needed because the standard model does not account for all forces, such as gravity, in the universe.

"What we wanted to do with these experiments was to say, 'Let's take a simple system – a single proton and a single antiproton – and let's compare their predicted relationships, and see if our predictions are correct," Gabrielse said. "Ultimately, whatever we learn might give us some insight into how to explain this mystery."

While researchers were able to capture and measure protons with relative ease, antiprotons are only produced by high-energy collisions that take place at the extensive tunnels of the CERN laboratory in Geneva, Gabrielse said, leaving researchers facing a difficult choice.

"Last year, we published a report showing that we could measure a proton much more accurately than ever before," Gabrielese said. "Once we had done that, however, we had to make a decision – did we want to take the risk of moving our people and our entire apparatus – crates and crates of electronics and a very delicate trap apparatus – to CERN and try to do the same thing with antiprotons? Antiprotons would only be available till mid-December and then not again for a year and a half.

"We decided to give it a shot, and by George, we pulled it off," he continued. "Ultimately, we argued that we should attempt it, because even if we failed, that failure would teach us something." In what Gabrielse described as a "gutsy" choice, graduate student Jack DiSciacca agreed to use this attempt to conclude his thesis research, and new graduate students Marshall and Marable signed on to help.

Though their results still fit within the predictions made by the standard model, Gabrielse said being able to more accurately measure the characteristics of both matter and antimatter may yet help shed new light on how the universe works.

"What's also very exciting about this breakthrough is that it now prepares us to continue down this road," he said. "I'm confident that, given this start, we're going to be able to increase the accuracy of these measurements by another factor of 1,000, or even 10,000."

Explore further: With neutrons, scientists can now look for dark energy in the lab

More information: physics.aps.org/articles/v6/36

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dschlink
5 / 5 (4) Mar 25, 2013
An important datum: "antiproton and proton magnetic moments differ by less than 5 parts per million, in agreement with the CPT theorem"

http://physics.ap...es/v6/36
axemaster
5 / 5 (3) Mar 25, 2013
In a breakthrough that could one day yield important clues about the nature of matter itself, a team of Harvard scientists have succeeding in measuring the magnetic charge of single particles of matter and antimatter more accurately than ever before.


have succeeding in measuring the magnetic charge of single particles of matter and antimatter


magnetic charge


No.
DarkWingDuck
3.3 / 5 (4) Mar 25, 2013
An important datum: "antiproton and proton magnetic moments differ by less than 5 parts per million, in agreement with the CPT theorem"

http://physics.ap...es/v6/36

Thank you... One would think that a science writer covering this would inlude the finale.
rkolter
not rated yet Mar 25, 2013
By precisely measuring the oscillations of each particle, the team was able to measure the magnetism of a proton more than 1,000 times more accurately than an antiproton had been measured before. Similar tests with antiprotons produced a 680-fold increase in accuracy in the size of the magnet in an antiproton.

This kind of hurt my brain. I hope they meant "1000 times more accurately than a proton had been measured before...", questioned why an anti-proton would only be able to be measured 680 times more accurately and not 1000 times more accurately, and kind of chuckled at the notion of "the size of the magnet in an anti-proton."

That aside, I liked the article and gave it a 5 for being about an interesting advance.

edit: kudos to dschlink for the link to the article. A good read.
mjlavall
1 / 5 (1) Mar 25, 2013
680-fold...that's probably not the correct figure
rkolter
not rated yet Mar 25, 2013
It could be. It's not unheard of to get a huge improvement in measurement. I don't dispute the magnitude of the improvement so much as I question why their apparatus was able to provide such an improvement to the measurement of the magnetic moment of a proton but not that of an anti-proton, when both particles are by their very nature identical save for their charge.

I can think of some probably valid reasons. I'd just like to know if those are accurate numbers, and if so, what reason they have for the discrepency.
vacuum-mechanics
1 / 5 (5) Mar 25, 2013
"One of the great mysteries in physics is why our universe is made of matter," he said. "According to our theories, the same amount of matter and antimatter was produced during the Big Bang. When matter and antimatter meet, they are annihilated. As the universe cools down, the big mystery is: Why didn't all the matter find the antimatter and annihilate all of both? There's a lot of matter and no antimatter left, and we don't know why."

Actually, what which was called as anti-particles, such as anti-electrons, was unstable, they were not found in all matter of our daily life world! Maybe it was just condensed energy with opposite state of electron, this is the reason why both they are annihilated in a burst of energy when meets each other. And maybe this paper could give some idea.
http://www.vacuum...=4〈=en
rah
1 / 5 (2) Mar 26, 2013
I guess it was too much to expect any specifics.
LarryD
not rated yet Mar 26, 2013
I enjoyed the article but more so the link from DarkWingDuck. But being an ignorant layman when I read the above article very quickly I thought 'what has Cumulative Prospect Theory [CPT] to with QM? Of course when I read it properly I found that I missed the (Charge conjugation, Parity transformation, Time reversal)part. Rather like QED and QED...Will I ever get used to it?
triplehelix
2.3 / 5 (3) Mar 26, 2013
I assume the reason measuring anti-protons is slightly less accurate is because you have to super speed collide particular particles to get an anti proton, this will cause noise, more noise than something which doesn't have to be collided at super speed. Assumedly then you need to use some heavy stat work to transform the figure into a workable "average" (Cant think of a better word here, I don't mean a literal average).

Just imagine weighing a ball bearing that's been clamped on a fine 7-8 place balance. Now weigh the same ball as its rolling round and round, the balances sensitivity will pick it up and cause "deviations" to the non rolling figures, meaning you have to make estimations and educated guesses (Very good ones) and you end up with slightly less accuracy (1000 vs 680).

This makes sense to me, I'm not stating this is the case but why I think it might be.
robeph
not rated yet Mar 26, 2013
Natello, we tire if this PETA nonsense, we're here trying to learn important information and these so called People for the Ethical Treatment of Antiparticles keep trying to stifle the research. It's ridiculous.

LarryD
not rated yet Mar 26, 2013
Natello, we tire if this PETA nonsense, we're here trying to learn important information and these so called People for the Ethical Treatment of Antiparticles keep trying to stifle the research. It's ridiculous.


Quite right! Maybe Natello can give me a link to where this idea came from...first I've heard of it.
Is it not possible that we are trying to solve a problem that wasn't there in the first place? The BB for example; being quite general about things doesn't an 'explosion' of any kind require some type of initial stimulus? In the case of BB the type of matter produced might depend on the condition of the 'singularity' at that particular moment and could it be that the stimulus might also determine the outcome? Just speculating.

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