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Is Supersymmetry Dead?

The grand scheme, a stepping-stone to string theory, is still high on physicists' wish lists. But if no solid evidence surfaces soon, it could begin to have a serious PR problem

If that proves not to be the case, one explanation is that heretofore underappreciated symmetries of the Standard Model keep the Higgs mass finite, as Bryan Lynn of University College London suggested last year. Others say Lynn’s idea would provide at best a partial explanation, leaving a vital role for physics beyond the Standard Model—if not super-symmetry, then one of the other strategies that theorists have devised. A popular plan B is that the Higgs boson is not an elementary particle but a composite of other par­ticles, just as protons are com­posites of quarks. Unfor­tunately, the LHC simply does not have enough data to say much about that idea yet, says CERN’s Christophe Grojean. More exotic op­tions, such as extra di­mensions of space beyond the usual three, may forever lie beyond the LHC’s reach. “Right now,” points out Gian Francesco Giudice, another theorist at CERN, “every single theory has its own problems.”

As ATLAS and CMS continue to accumulate data, they will either discover superparticles or exclude wider ranges of possible masses. Although they may never be able to strictly disprove super­symmetry, if the collider fails to find it, the theory’s usefulness may fade away, and even its most hard-core supporters may lose interest. That would be a blow not just to supersymmetry but also to even more ambitious unified theories of physics that presume it, which include string theory and other approaches [see “Loops, Trees and the Search for New Physics,” by Zvi Bern, Lance J. Dixon and David A. Kosower]. LHC physicists take this uncertainty in stride and expect the collider to find some new and exciting physics—not just the physics theorists had expected. Hinchliffe says, “The most interesting thing we will see is something that nobody thought of.”

This article was published in print as "Is Supersymmetry Dead?"

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