The Large Hadron Collider is the latest attempt to move fundamental physics past the frustratingly successful ‘standard model’. But it is not the only way to do it. Geoff Brumfiel surveys the contenders attempting to capture the prize before the collider gets up to speed.
While the LHC gets its protons up to speed, the world’s other heavyweight particle-accelerator is racing to break the standard model first. Since 2001, the Tevatron, located at Fermilab in Batavia, Illinois, has been accelerating protons and antiprotons at an energy of around 1 tera electron volt.
That’s only a seventh of the eventual top energy of the LHC, but total energy isn’t everything in the hunt for new physics. Collisions that would generate new particles outside the standard model are extremely rare, which means that the longer an accelerator runs and the more data it accumulates, the better its chances of finding something. So for a while, at least, the Tevatron will continue to have a data lead over the LHC. Even by the summer of 2009, the Tevatron will have several times more total data than its new competitor.
And already those data are showing some tantalizing, if tentative, hints of something beyond the standard model. One deviation comes in measurements of a particle known as the strange B (Bs) meson. The Bs is made of a strange quark and an anti-bottom quark, and it is among the heaviest of all mesons. Under a rule known as charge-parity symmetry, the standard model predicts the Bs will decay in the same way as its antiparticle (made of an anti-strange and a bottom quark). But measurements of the two are hinting at a difference in their decays. According to Dmitri Denisov, a spokesperson for the D-Zero experiment at the Tevatron, that difference could be an important clue in the quest for discoveries. It might signal the existence of new, exotic particles, or of previously unknown principles. In any case, says Denisov, “it’s an exciting measurement”.