A New Era of Physics at the Large Hadron Collider

Article excerpt

Last month in Washington, D.C., at the annual meeting of the American Association for the Advancement of Science, theoretical physicist Lisa Randall of Harvard University spoke about her hopes for the Large Hadron Collider, the world's most powerful particle accelerator. She sat down with Science News physical sciences writer Devin Powell after her February 19 talk to discuss what evidence the European collider, which is expected to operate at half power through 2012, might provide for her groundbreaking theories and for the Higgs mechanism, a process that would explain why particles have mass.

You've said that physics is entering a "new era." What do you mean by that?

At the high energies of the LHC, you're getting very precise, and you're getting to, in some sense, simpler systems where you can see the more basic and more fundamental rules of physics going on.... Studying higher energies is the same as studying smaller scales. We have this target scale, the weak energy scale that the LHC is exploring--that is to say, the scale at which we know particles are somehow acquiring mass associated with the Higgs mechanism.

Explain the theory that you and Raman Sundrum developed to resolve the "hierarchy problem," namely that gravity is much weaker than quantum physics would predict.

The scenario we had in mind is that some stuff is stuck on an object called a brane, which exists in three dimensions, but there can be an extra dimension of space where gravity can be concentrated away from us. That would explain why gravity is so weak for us.... By an extra dimension, I really do mean another dimension beyond the three we're familiar with: left-right, up-down and top-bottom. These extra dimensions are hidden somehow and part of the question is: Why are they hidden? They could be small or very warped.

What would you be most excited to see in the LHC's detectors?

It would be extremely exciting if they saw evidence for our theory, which would consist of a particle that is called the Kaluza-Klein partner of the graviton. You'd see something that looks like a graviton, which communicates gravity, but it would really be from an extra dimension.

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If the LHC finds a Kaluza-Klein particle, what does that mean for the Higgs mechanism and string theory?

The Higgs could be there whether or not there are extra dimensions. …