Particle Probing Goes Pear Shaped

The question that has vexed scientists and astronomers for years is why there is more matter in the Universe than antimatter. 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 carried out at the Institut Laue-Langevin (ILL), Grenoble, France, with its high flux reactor. 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.

ILL’s Peter Geltenbort explains: “This represents a significant breakthrough, and a real success for particle physics using neutrons…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.

Philip Harris and Maurits van der Grinten, of Sussex University and Rutherford Appleton Laboratory (RAL) in the UK, worked in conjunction with the ILL. 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 that will submerge their neutron-clock in a bath of liquid helium, half a degree above absolute zero, they hope to increase their sensitivity a hundredfold.

Adapted from an ILL Press Release

3 thoughts on “Particle Probing Goes Pear Shaped”

  1. Why oh why isn’t there any antimatter in my soup? Well, perhaps the issue one should be looking at is TIME. How many times have you heard that antimatter can be thought of as matter traveling backwards through time?

    If so, then wouldn’t one have to conclude that antimatter is created in the far future, indeed at the end of time as we know it? Kinda like that Star Trek: The Next Generation series finale which did the whole reverse time thing, but more so.

    There would be more matter in the early universe, since most of it would not yet have encountered antimatter from the future. As time passes, more and more matter and antimatter annihilate- in the far future antimatter outweighs matter. In between is a matter/antimatter minimum.

    BUT, there is an interesting twist. If the universe is closed (the whole go round the universe and come back to where you started thing) then time must partake in this as well. That means that the end of time is also the beginning of time. Think of time, then, as a circle.

    At time 0 matter and antimatter coalesce from the initial ‘bang’ but go in opposite temporal directions. This isn’t a big deal, since before matter per se there isn’t anything for antimatter to annihilate with, and so it passes temporally right through the singularity and goes into negative time. Negative time is then coming back at us from the future, from our perspective time 1 (i.e. 100%).

    At time .5 these two temporal paths interact with each other maximally, and we see the greatest interactive equalization, whatever that means.

    Obviously it has to be more complicated than this, but it may give some bright boy out there food for thought, to debunk or build up. The time gap between the singularity and enough symmetry breaking to produce matter is for me the most interesting area to look at, and should have a matching gap on the negative time side.


  2. Fascinating conjecture…

    Maybe that is all the Big Bang was, is, will be…the point at which matter and antimatter head off in different directions around that unimaginably huge “circle”…

  3. This is four and a half years after that original post. It now looks as if the matter/anti-matter problem may be related to some factors that were not considered at that time, as a new approach called the Oscillator-Substance Model suggests that the anti-matter/matter situation may be almost a matter of semantic confusion, as by one set of logical inferences, “protons” which are considered the “major mass units of Matter,” may be considered by another definition as “Anti-matter!”

    From the same model comes the idea that the “Big Bang” would correspond to an inversion or splitting of an oscillator, producing two halves. This is close to the “backwards in time” ideas in the earlier comments, the idea here is simply opposite vectors in space….

    A third view also comes from O/S is that the neutron count of an atomic nucleus actually is a count of the units which at a given instant may be considered as being in an “Anti-matter state,” at any given instant. That is, if we consider anti-matter as made up of positrons and anti-protons.

    Again from O/S Model comes the idea that the neutron would be deformed slightly by the fact of its being an oscillator which is operating within other oscillators including the one which we call our Universe which has a rotation and expansion ….

    Most of the O/S information is summarized on

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