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"Perfect" Electron Roundness Bruises Supersymmetry
astroengine writes "New measurements of the electron have confirmed, to the smallest precision attainable, that it has a perfect roundness. This may sounds nice for the little electron, but to one of the big physics theories beyond the standard model, it's very bad news. 'We know the Standard Model does not encompass everything,' said physicist David DeMille, of Yale University and the ACME collaboration, in a press release. 'Like our LHC colleagues, we're trying to see something in the lab that's different from what the Standard Model predicts.' Should supersymmetrical particles exist, they should have a measurable effect on the electron's dipole moment. But as ACME's precise measurements show, the electron still has zero dipole moment (as predicted by the standard model) and is likely very close to being perfectly round. Unfortunately for the theory of supersymmetry, this is yet another blow."
http://www.youtube.com/watch?v=hhbqIJZ8wCM
radius: 2.8179403267e-15 m
surface: 9.9786881e-29 m^2
volume: 9.3731159e-44 m^3
above in fuzzy logic: very tiny
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much of left-wing thought is a kind of playing with fire by people who don't even know that fire is hot - George Orwell
The deviations they are talking about aren't things like mountains or bumps, but a systematic non-spherical bias.
For example, the earth isn't spherical either, it's basically a bit fatter around the equator pretty close to an oblate spheroid (e.g., an M&M is a more exaggerated oblate spheroid). Like a baseball, if the electron isn't totally spherical, you can detect a systematic bias as it's being thrown around (you can think of the LHC as throwing an electron spit-ball or a knuckle-ball).
Although even in the standard model, the electron at some energy level probably has a detectable dipole moment (e.g., the charge wouldn't be uniformly spherically distributed in the electron), it is my understanding that it is predicted to be too small to be validated by current experiments. However, some versions of super-symmetry apparently would predict that the electron at some energy levels would have a larger detectable dipole moment . I guess these super-symmetry predictions didn't pan out.
radius: 2.8179403267e-15 m
That is the classical answer. It is generally considered to be a point particle today.
It's a little more involved. We know that the standard model is unable to explain a few important observations (such as gravity) so it *can't* be the whole story. Any theory that accounts for gravity and dark matter/energy will be more elegant by virtue of not having holes in it.
Supersymmetry could explain those things and fortunately makes a few predictions that we are now capable of testing. However, those aren't panning out so it must be revised and tested again. At least until someone comes up with something better to test.
http://en.wikipedia.org/wiki/Supersymmetry
A whole lot of PhD dissertations, physics publications, and academic careers are on the line over this. String theory is the current favorite and loop quantum gravity the underdog. The direction of theoretical particle physics could be radically altered if the LHC doesn't find evidence of supersymmetry.
Why is Snark Required?
Yes in a way you are correct.
"Thus, at non-relativistic energies the EDM [electric dipole moment] corresponds to a shift of energy levels of the electron in an external electric field E that depends on the direction of electron's spin Se. "
More details:
http://resonaances.blogspot.com.au/2013/11/electric-dipole-moments-and-new-physics.html
This is a good question. There are a number of theoretical and empirical motivations for supersymmetry, including the existence of dark matter, the matter-antimatter asymmetry in the universe, and the hierarchy problem in particle physics. I don't fully understand all of these myself. However, this short video released by my collaboration tries to explain some of them at a basic level: http://www.youtube.com/watch?v=UIflReRmynk.
It says that supersymmertry predicts a larger dipole moment, that's why it would be in question.
If you want to know why supersymmetry makes that prediction then you aren't going to get that in a new article or a slashdot post. There are lots of resources available for learning SUSY, or jump in the deep end with something random like http://www.springer.com/physics/particle+and+nuclear+physics/book/978-4-431-54543-9