Monday, February 13, 2012

LHC boosts energy to snag Higgs – and superpartners

No hiding place, Higgs <i>(Image: Simon Hadley/Rex Features)</i>
No hiding place, Higgs (Image: Simon Hadley/Rex Features)

It has already broken the record for the most energetic particle collisions, but the world's largest particle smasher is boosting its energy still further. Physicists at the Large Hadron Collider hope this will confirm or rule out tantalising hints of the elusive Higgs particle.
Although the Higgs is the LHC's main quarry, the biggest advantage from the boost in energy goes to searches for signs of supersymmetry, or SUSY. Many researchers had hoped that by now this elegant theory would have left traces in LHC, which is at the CERN particle physics laboratory near Geneva, Switzerland.
The LHC has already seen many events that could be signs of the decay of the long-sought Higgs boson, which is thought to endow other particles with mass. But more mundane reactions can also produce such events, so more experiments are needed to confirm or rule out the Higgs explanation.
Now the LHC's management has decided to boost the energy of collisions to get a better chance of flushing the Higgs out into the open.

Higgs boost

Last year, the LHC smashed two beams of protons together at an energy of 3.5 teraelectronvolts (TeV) each, resulting in collisions with a total energy of 7 TeV.
The machine's managers have decided to increase the energy of collisions to 4 TeV per beam, for a total energy of 8 TeV.
The probability of a collision producing heavy particles rises very fast as its energy increases, so even a small rise in energy will provide a big boost to the number of Higgs bosons made – and therefore the probability of glimpsing them or other exotica.
Running at 8 instead of 7 TeV should boost the machine's sensitivity to Higgs particles – assuming they are really there – by 30 to 40 per cent, says Greg Landsberg of Brown University in Providence, Rhode Island, who is involved in CMS, one of the LHC's two main detectors.

Heavy partners

The boost in energy also increases the chances that signs of SUSY will emerge.
The theory posits the existence of heavy partners for each of the subatomic particles already known. The move to 8 TeV could boost the production of these "superpartners" as much as four times, says Landsberg.
"We could get a little hint of existence at 7 TeV versus discovery at 8 TeV," he says.
Researchers want to maximise the potential for new discoveries this year because at the end of it the LHC will shut down for two years. Upgrades will then allow it to run at its full design energy of 14 TeV.
The Higgs boson should have already been confirmed or ruled out before then. The higher energy will allow a thorough search for the heavy particles predicted by SUSY, among other things.

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