Thursday, January 24, 2008

Higgs Hiding in Plain Sight?

Could the Higgs already have been discovered and no one knew it?

Not likely, but with a headline like that, who can resist reading it? A Science news article reports on a paper that proposes that a very light "Higgs" may already be in the data as far back as the LEP at CERN, and could be hiding in the data from the Tevatron.

But experimenters may have already overlooked a Higgs particle, argues theorist Chien-Peng Yuan of Michigan State University in East Lansing and his colleagues. They considered the simplest possible supersymmetric theory. Ordinarily, theorists assume that the lightest of theory's five Higgses is the one that drags on the W and Z. Those interactions then feed back on Higgs and push its mass above 121 times the mass of the proton, the highest mass searched for at CERN's Large Electron-Positron (LEP) collider, which ran from 1989 to 2000. But it's possible that the lightest Higgs weighs as little as 65 times the mass of a proton and has been missed, Yuan and colleagues argue in a paper to be published in Physical Review Letters.

Unfortunately, this may not be the Higgs that everyone is looking for. It seems that this Higgs does not endow any mass to the W and Z, since it doesn't couple to them.

However, this lightweight Higgs is not exactly the Higgs everyone is looking for, says Marcela Carena, a theorist at Fermilab. "The Higgs they are talking about is not the one responsible for giving mass to the W and Z," she says. It can't be because it hardly interacts with those particles, Carena says. Indeed, in Yuan's model, the role of mass-giver falls to one of the heavier Higgses, which is still heavier than the LEP limit, she notes.



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