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Interactions News Wire #14-06
20 February 2006 http://www.interactions.org
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Source: ILL
Content: Press Release
Date Issued: 20 February 2006
*******************************************************************
Bouncing pear-shaped particles probe the mystery of the big-bang:
an experiment carried out at the ILL in Grenoble
An international team of scientists has just announced the long-awaited results of the quest for the most sensitive measurements ever of sub-atomic particles: why the Universe contains the matter that we're made of? Theories attempting to explain the creation of matter in the aftermath of the Big Bang now have to be tuned up - or even thrown out.
The question that has vexed scientists and astronomers for years is why there is more matter in the Universe than anti-matter. Both were formed at the time of the Big Bang, about 13.7 billion years ago. For every particle formed, an anti-particle should also have been formed. Almost immediately, however, the equal numbers of particles and anti-particles would have annihilated each other, leaving nothing but light. But a tiny asymmetry in the laws of nature resulted in a little matter being left over, spread thinly within the empty space of the Universe. This matter became the stars and planets that we see around us today.
Experiments have been carried out at the Institut Laue-Langevin (ILL), Grenoble, France, with its high flux reactor. At an instrument unique in the world, neutrons produced in the reactor can be slowed down and then stored in special traps where they bounce around like ping pong balls. This allows long observation times and hence experiments on the fundamental properties of the neutron of outstanding accuracies.
The new result shows that the distortion in these subatomic particles is far smaller than most of the origin-of-matter theories had predicted. In relative terms, it's less than the size of a bacterium sitting on an Earth-sized neutron would be.
Physicist Dr. Peter Geltenbort of the ILL says: “This represents a significant breakthrough, and a real success for particle physics using neutrons. The result underlines the first class experimental facilities available at the ILL. Over the years the method has been improved steadily, and pushed to its limits. It's been said in the past that this experiment has disproved more theories than any other in the history of physics -and now it's delivering the goods all over again."
The only way scientists can verify their theories to explain this anomaly is to study the corresponding asymmetry in sub-atomic particles, by looking for slight "pear-shaped" distortions in their otherwise spherical forms. It has taken five decades of research to reach the stage where measurements of these particles, called neutrons, have become sensitive enough to test the very best candidate theories. Neutrons are electrically neutral, but they have positive and negative charges moving around inside them. If the centres of gravity of these charges aren't in the same place, it would result in one end of the neutron being slightly positive, and the other slightly negative. This is called an electric-dipole moment, and it is the phenomenon that physicists have been working to find for the past 50 years. Spin-offs from the original pioneering work in this area include atomic clocks and magnetic-resonance imaging.
The apparatus employed a special type of atomic clock that used spinning neutrons instead of atoms. It applied 120,000 volts to a quartz "bottle" that was filled regularly with neutrons captured from a reactor. The clock frequency was measured through nuclear magnetic resonance.
Physicists Dr Philip Harris and Dr Maurits van der Grinten, respectively heading the groups at Sussex University and Rutherford Appleton Laboratory (RAL) in the UK, emphasize: “Although there are a couple of other teams in the world working in this same area, we’re managing to stay ahead of them, and we are constantly striving to beat our own world record.” The Sussex and RAL groups worked in conjunction with the ILL, where the experiment took place. The team has now expanded to include Oxford University and the University of Kure in Japan. They are busy developing a new version of the experiment which will again be located at the ILL: by submerging their neutron-clock in a bath of liquid helium, half a degree above absolute zero, they hope to increase their sensitivity a hundredfold.
[Paper submitted to Physics Review Letters, available as preprint hep-ex/0602020]
Françoise Vauquois,
press officer
ILL
+33 4 76 20 71 07
20 February 2006 http://www.interactions.org
*******************************************************************
Source: ILL
Content: Press Release
Date Issued: 20 February 2006
*******************************************************************
Bouncing pear-shaped particles probe the mystery of the big-bang:
an experiment carried out at the ILL in Grenoble
An international team of scientists has just announced the long-awaited results of the quest for the most sensitive measurements ever of sub-atomic particles: why the Universe contains the matter that we're made of? Theories attempting to explain the creation of matter in the aftermath of the Big Bang now have to be tuned up - or even thrown out.
The question that has vexed scientists and astronomers for years is why there is more matter in the Universe than anti-matter. Both were formed at the time of the Big Bang, about 13.7 billion years ago. For every particle formed, an anti-particle should also have been formed. Almost immediately, however, the equal numbers of particles and anti-particles would have annihilated each other, leaving nothing but light. But a tiny asymmetry in the laws of nature resulted in a little matter being left over, spread thinly within the empty space of the Universe. This matter became the stars and planets that we see around us today.
Experiments have been carried out at the Institut Laue-Langevin (ILL), Grenoble, France, with its high flux reactor. At an instrument unique in the world, neutrons produced in the reactor can be slowed down and then stored in special traps where they bounce around like ping pong balls. This allows long observation times and hence experiments on the fundamental properties of the neutron of outstanding accuracies.
The new result shows that the distortion in these subatomic particles is far smaller than most of the origin-of-matter theories had predicted. In relative terms, it's less than the size of a bacterium sitting on an Earth-sized neutron would be.
Physicist Dr. Peter Geltenbort of the ILL says: “This represents a significant breakthrough, and a real success for particle physics using neutrons. The result underlines the first class experimental facilities available at the ILL. Over the years the method has been improved steadily, and pushed to its limits. It's been said in the past that this experiment has disproved more theories than any other in the history of physics -and now it's delivering the goods all over again."
The only way scientists can verify their theories to explain this anomaly is to study the corresponding asymmetry in sub-atomic particles, by looking for slight "pear-shaped" distortions in their otherwise spherical forms. It has taken five decades of research to reach the stage where measurements of these particles, called neutrons, have become sensitive enough to test the very best candidate theories. Neutrons are electrically neutral, but they have positive and negative charges moving around inside them. If the centres of gravity of these charges aren't in the same place, it would result in one end of the neutron being slightly positive, and the other slightly negative. This is called an electric-dipole moment, and it is the phenomenon that physicists have been working to find for the past 50 years. Spin-offs from the original pioneering work in this area include atomic clocks and magnetic-resonance imaging.
The apparatus employed a special type of atomic clock that used spinning neutrons instead of atoms. It applied 120,000 volts to a quartz "bottle" that was filled regularly with neutrons captured from a reactor. The clock frequency was measured through nuclear magnetic resonance.
Physicists Dr Philip Harris and Dr Maurits van der Grinten, respectively heading the groups at Sussex University and Rutherford Appleton Laboratory (RAL) in the UK, emphasize: “Although there are a couple of other teams in the world working in this same area, we’re managing to stay ahead of them, and we are constantly striving to beat our own world record.” The Sussex and RAL groups worked in conjunction with the ILL, where the experiment took place. The team has now expanded to include Oxford University and the University of Kure in Japan. They are busy developing a new version of the experiment which will again be located at the ILL: by submerging their neutron-clock in a bath of liquid helium, half a degree above absolute zero, they hope to increase their sensitivity a hundredfold.
[Paper submitted to Physics Review Letters, available as preprint hep-ex/0602020]
Françoise Vauquois,
press officer
ILL
+33 4 76 20 71 07