The BaBar Experiment

The BaBar experiment is looking for CP violation in B mesons. Current theory predicts that it should be more pronounced than in kaons.

So what does this have to do with the puzzle of the missing antimatter? Well, there is a third way of tinkering with the laws of physics - time reversal (T). Just as physicists thought the equations should look the same if you replace +x with -x, they should also look the same if you replace +t with -t. However, they found that this is not the case.

The combination of CP and T must be conserved. If CPT is violated then we really do have problems. Now, we know CP is violated for kaons. This means that T must also be violated, otherwise the combination of CP and T cannot be conserved.

This gives us another way of looking at the kaons' dance. CP violation means that if you look at the dance in a mirror and swap the and , then the dance does not look quite the same. Similarly, if you were to film the dance and then play it backwards it would not look quite the same.

The upshot of all this is that it implies that matter and antimatter do not evolve in time in quite the same way. This is important because it suggests that the laws of physics are not quite the same for matter as they are for antimatter. This in turn may go some way towards explaining the predominance of matter over antimatter in the Universe today.

Although the Standard Model predicts CP violation, it only predicts it at a very small level - not enough to account for the absence of antimatter. If BaBar confirms that CP violation is that small, then we need to come up with a new idea to explain the lack of antimatter. If, on the other hand, BaBar finds a greater effect, our current theories will have to be altered to explain why the effect is so large. Either way we cannot lose - there is bound to be new physics discovered as a result of the BaBar experiment.

This concludes the discussion of the background physics. Click here to find out more about the experiment itself.

Last modified Tue 11 April 2000 . View page history
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