Friday, December 27, 2013

139.7 - And Another Thing #3: looking for lumpy electrons

And Another Thing #3: looking for lumpy electrons

Okay, I saved what I think is the coolest for last.

We have to start with two things. First, we're used to thinking of electrons as those little thingies that orbit the nucleus of an atom. Never mind shells and clouds and superposition and all that for now, just focus on the thingies.

With the wonderful duality at the heart of quantum physics, elections can be regarded as point particles, with no dimensions. But they can also be thought of as very, very tiny spheres.

Okay, the second thing is that there is a flaw hidden in the so-called Standard Model of particle physics. The Big Bang, the start of the observable universe, should have produced equal numbers of particles and anti-particles. But identical particles and anti-particles annihilate each other back to pure energy. So we shouldn't be here. Obviously, that didn't happen, because we are here, and the question is why: Why were there more particles than anti-particles? The difference didn't have to be big, but it did have to exist. The Standard Model can't be all there is.

There are several hypotheses that look to go beyond the Standard Model to try to answer that question and figure out just what it is that we are missing in our understanding of the fundamental nature of the universe.

An experiment sitting in a large basement room off of Oxford Street in Cambridge has been trying to probe that question by measuring, get this now, the lumpiness of electrons.

See, the Standard Model says that electrons must be perfect or nearly perfect spheres. But a number of the hypotheses that seek to go beyond the Standard Model predict the existence of undiscovered massive particles that would distort an electron's electric dipole moment. Don't worry if you don't understand that; simply, the "electric dipole moment" describes the distribution of the negative electric charge within that electron. The point is, that negative charge is the electron, so if the distribution of charge and so the electric dipole moment is distorted, the electron will not appear to be a perfect sphere; it will appear to be "lumpy." So by measuring that dipole moment, the researchers are looking for indirect evidence of these undiscovered particles.

The experimental team, consisting of scientists from Harvard and Yale, has been able to measure an electron's electric dipole moment to a degree of accuracy an order of magnitude - that's ten times - greater than ever before.

How accurate? The team said "Imagine an electron blown up to the size of the earth. Our experiment would have been able to see a layer ten thousand times thinner than a human hair, moved from the southern to the northern hemisphere."

And the result? The electron stubbornly appears to be a perfect sphere, which would be bad news for a number of those hypotheses, including one popular one known as Weak Supersymmetry.

It may be that the distortion of the electron is still smaller than the experiment could detect and the team is looking to increase the sensitivity of their experiment. But for the moment, what remains is that we can run exquisitely fine experiments - we're measuring the "lumpiness" of electrons, for pity's sake - which have given us an exquisitely fine understanding of the nature of reality. But there is still something missing, something we don't understand, something more to discover. And in science, that is the ultimate cool.


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