Physicists Trap a Single Antimatter Particle For a Month (yahoo.com) 44
Physicists at Northwestern University have successfully trapped a single positron for an entire month, allowing researchers to study its quantum properties with unprecedented precision. "Further investigations using the trap might reveal the secret of why the world around us is made of matter and not antimatter, when things could have presumably gone either way," reports Scientific American. From the report: Every normal particle of matter has an antimatter counterpart with equal mass but opposite charge. To build their trap, physicists started with atoms of sodium 22, a radioactive isotope with a half-life of about two and a half years. When one of these atoms decays, it emits a positron -- the antimatter counterpart of the electron. "The big challenge is to persuade these positrons to slow down and then capture them," says Gerald Gabrielse, a physicist at Northwestern University, who oversaw the project. The team reported its achievement on Wednesday in Physical Review Letters (PDF).
The first step is to send the positrons through the crystal lattice of a sliver of cold tungsten. As the particles go pinballing through the material, they slow down and lose energy. "Every time they bang into something, there's a chance of annihilation, but it doesn't always happen," Gabrielse says. "If they make it to the end, they get popped out." Next, the physicists steer the positrons along a channel using electromagnetic fields. Eventually the particles end up in a vacuum, just three tenths of a degree Celsius above absolute zero, trapped by an electric field on top and bottom and a magnetic field on the sides. "If you want to hold on to antimatter, you have to hold it in a container without walls," Gabrielse says. This method allowed the researchers to isolate and study a solitary, lone positron for a monthâ"and could let them do so indefinitely.
The researchers intend to use their trap to make precise measurements of the positron's magnetic moment -- basically the strength and orientation of its magnetic field. To do this, they must determine two things: the energy needed to flip the direction of the positron's spin and the energy needed to make it jump from its ground state to its first excited state. Using a similar trap setup, Gabrielse and his team have already measured the magnetic moment of an electron to a precision of one part in 10 trillion. Taking the equivalent measurement for a positron will allow them to make a crucial comparison. "We're looking to see if they have an exactly opposite magnetic moment," Gabrielse says. That's the prediction of the Standard Model of particle physics. If the two have different values, however, this could help explain why our universe is made of matter instead of antimatter.
The first step is to send the positrons through the crystal lattice of a sliver of cold tungsten. As the particles go pinballing through the material, they slow down and lose energy. "Every time they bang into something, there's a chance of annihilation, but it doesn't always happen," Gabrielse says. "If they make it to the end, they get popped out." Next, the physicists steer the positrons along a channel using electromagnetic fields. Eventually the particles end up in a vacuum, just three tenths of a degree Celsius above absolute zero, trapped by an electric field on top and bottom and a magnetic field on the sides. "If you want to hold on to antimatter, you have to hold it in a container without walls," Gabrielse says. This method allowed the researchers to isolate and study a solitary, lone positron for a monthâ"and could let them do so indefinitely.
The researchers intend to use their trap to make precise measurements of the positron's magnetic moment -- basically the strength and orientation of its magnetic field. To do this, they must determine two things: the energy needed to flip the direction of the positron's spin and the energy needed to make it jump from its ground state to its first excited state. Using a similar trap setup, Gabrielse and his team have already measured the magnetic moment of an electron to a precision of one part in 10 trillion. Taking the equivalent measurement for a positron will allow them to make a crucial comparison. "We're looking to see if they have an exactly opposite magnetic moment," Gabrielse says. That's the prediction of the Standard Model of particle physics. If the two have different values, however, this could help explain why our universe is made of matter instead of antimatter.
Charges must be brought (Score:5, Funny)
Antimatter half-lives matter.
Re: Charges must be brought (Score:5, Funny)
But only half.
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Of course, which makes this whole thing so much worse! They didn't feed it!
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Free the particle!
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Someone paid the ransom.
Nice. Now when can I buy ... (Score:2)
... Anti-Matter Grenades?
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... Anti-Matter Grenades?
If you set one of those off in the woods, do the people not there make a sound?
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Enterprise (Score:2)
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When your starship will run on one anti-matter atom.
Actually, anti-matter factories are possible, but probably not in a strong gravity field surrounded by positive matter. (Also they aren't cheap to power. It takes a lot of power to create mass, and you need to create twice as much as the amount of anti-matter you end up with, even if you get 100% efficiency.)
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Does it anti matter? (Score:2)
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LoB
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Explains Bruce Banner's pants.
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Actually, I think CPT invarience means there is a difference. But this only applies to weak-force interactions.
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That explains Mister Fantastic and Helen Parr.
Re:Does it anti matter? (Score:5, Funny)
Stop being so negative.. I mean positive.
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Say the universe was made of antimatter instead of matter, would we not have just called that matter and then matter would be anti and everything else be pretty much the same apart the charge?
Before this experiment, yes.
That still wouldn't keep the anti-slashdotters from bitching that science was wrong back before scientists looked for and gave an answer though.
Would we even be able to tell the difference?
That's exactly the question this experiment was created to answer.
Initial results indicate "Yes" there is a difference, but they want to finish analyzing the results to make sure it wasn't a fluke.
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Trapped antimatter (Score:4, Funny)
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Free antimatter with every matter
So... (Score:2)
...positronic Robots real soon now?
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For a month? (Score:2)
But if relatives came forth with authentic requests for petition, etc would homeland security stand down
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What if Antimatter is a social species... (Score:2)
How do they know? (Score:2)
How can a single positron be detected and tracked when there are billions and billions of other particles all around? What kind of sensors are they. Find it too hard to digest.
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They're quite positive.
normal matter decay produces antimatter? (Score:3)
I'm curious how the nuclear decay of sodium 22 produces antimatter to begin with. Does something transmute, for lack of a better word, into antimatter when its nuclear bonds are broken?
Re:normal matter decay produces antimatter? (Score:4, Informative)
It is called beta plus decay, the opposite of a beta minus. In beta minus, a neutron decays into a proton and an electron, which has the proton charge (and also an anti-neutrino, which conserves the lepton charge of the electron). In beta plus, this is reversed, a proton decays to a neutron, emits a positron (preserves electric charge) and a neutrino (negates the anti-lepton charge of the emitted positron).
Or somesuch.
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I'm curious how the nuclear decay of sodium 22 produces antimatter to begin with. Does something transmute, for lack of a better word, into antimatter when its nuclear bonds are broken?
Bananas create anti matter. From Ten things you might not know about antimatter [ihep.cas.cn] (also mentioned, but not explained here DOE Explains...Antimatter [energy.gov]) :
Bananas produce antimatter, releasing one positron—the antimatter equivalent of an electron—about every 75 minutes. This occurs because bananas contain a small amount of potassium-40, a naturally occurring isotope of potassium. As potassium-40 decays, it occasionally spits out a positron in the process.
States (Score:2)
make it jump from its ground state to its first excited state.
I thought this energy level for state transitions depended on which orbital they occupied (using an analogy with electrons).
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So, they are measuring the properties of the positron interacting with the magnetic bottle (under the assumption that there is no anti-nucleus involved).
Duh (Score:2)
why the world around us is made of matter and not antimatter
Because that's what matters.