Thursday, May 10, 2007

Large Hadron Collider

Elizabeth Kolbert has a really great article in the New Yorker on the Large Hadron Collider. So far physicists have successfully observed 16 types of elementary particles (together with their anti-particles and sub-types) predicted by the standard model of particle physics. The standard model predicts a 17th particle: the Higgs boson. The Higgs has never the experimentally observed. However, it is crucial to the standard model. As the article notes:

Without the Higgs, physicists have no way to explain why fundamental particles weigh anything at all, since, according to theory, they should be massless.

The Higgs boson is a "massive" particle and requires enormous energies to be created. The Large Hadron Collider (LHC) is able to accelerate protons up to
99.9999991% of the speed of light around a circular tunnel with a 17 mile circumference. This corresponds to the protons having an energy of 7 TeV (tera electron volts), and the resulting collisions should have enough energy to create the Higgs. In addition:

It may also be enough to uncover much more than the Higgs. Depending on how the universe is constructed, extra dimensions, mini black holes, and the source of so-called “dark matter” may all be revealed ...

All very esoteric and cool! (We are assured that the mini blackholes will be "...entirely benign..."!)

The engineering of the LHC is equally remarkable. It uses superconducting magnets to keep the protons on the circular path. These magnets are cooled to -271.25 Celsius---that's 0.10 degrees above absolute zero! There are four sets of detectors around the track, each set developed by a different team of scientists. These are supposed to detect any trace of the Higgs and these other esoteric byproducts of the collision. The data analysis task to actually identify these byproducts is equally daunting (" finding a needle in a needle factory").

The LHC is very expensive: some $8 billion. Funding of this sort is hard to come by for ventures with no practical implications. So there is a lot riding on its success. Kolbert ends her article with:

The promise of the Large Hadron Collider is thus also its great burden. A truly astonishing discovery there—proof, say, of extra dimensions, or of something even weirder than that, which theorists have yet to conceive of—would provide a powerful impetus to keep particle physics going for another generation. Barring a breakthrough, it’s hard to imagine how the project can continue. Such an outcome would not mean that the fundamental order of the universe is unknowable. But it might well mean that we will never know it.

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