Particle physicists have ruled out one of the possible remaining hiding places of the Higgs boson, bringing them one step closer to finding the slippery subatomic particle–or, conceivably, to ruling out its existence.
Physicists believe that the Higgs particle interacts with some other particles, like the W and Z bosons, to give them mass. The standard quip about the Higgs is that it is the “God Particle” — it is everywhere but remains frustratingly elusive. Confirming the Higgs would fill a huge gap in the so-called Standard Model, the theory that summarizes our present knowledge of particles [AFP].
The new results, from the Tevatron particle accelerator at the Fermi National Accelerator Laboratory, narrow down the range of masses where the Higgs boson may be found. Physicist Craig Blocker explains that particle accelerators smash particles together and then sift through the debris produced, looking for particles with certain masses. Previous collider experiments had placed a lower bound of 114 giga-electron volts (GeV), a measure that can be used for particle mass, on the Higgs, and theoretical calculations require it to be less than 185 GeV. The new Fermilab results, from its Tevatron collider, rule out a Higgs mass between 160 and 170 GeV…. “If the Higgs had a mass in this fairly narrow range” of 160 to 170 GeV, he says, “we should have seen it, we had a good chance to see it” [Scientific American].
The Large Hadron Collider is widely expected to find the Higgs boson when it’s fully operational (the LHC started up with much fanfare in the fall, but an accident forced it to shut down for repairs until September of 2009). Researchers say that the new results mean that the LHC won’t have a quick route to success. The LHC was designed to collide particles with five times the energy of the Tevatron, and would have excelled at hunting for a high-mass Higgs particle. “If the Higgs existed at one of those high masses, then they could have anticipated discovering it very quickly,” says Darien Wood [Nature News], a particle physicist who works with the Tevatron.
It’s possible that the Tevatron will find a low-mass Higgs before the LHC comes back online, but most researchers say the more powerful LHC is still most likely to discover the elusive particle. But there is one other slim possibility–that the colliders will rule out all the possible masses for the Higgs boson, and still won’t find it. “That would basically mean we have a very deep and fundamental lack of understanding of what is going on in the Standard Model,” [physicist Craig] Blocker says. “If there’s not something like the Higgs or something similar giving masses to the W and Z [bosons], we have no clue as to how that’s happening” [Scientific American].
Cosmic Variance: Closing in on the Higgs Boson has more details on the latest findings
80beats: Until Next Fall, LHC Smashes Only Hopes, Not Particles
80beats: Ghost in the Machine? Physicists May Have Detected a New Particle at Fermilab
DISCOVER: Catch Me If You Can charts the search for the Higgs boson
DISCOVER: The Biggest Thing in Physics explains the LHC’s two approaches to finding the Higgs