Hunting the Higgs

By Michael Banks in Boston

“It looks like a Standard Model Higgs,” remarks Christopher Hill from Ohio State University. “Everything we have measured has strengthened that position.”

Last year, researchers working at the Large Hadron Collider (LHC) at CERN reported they had found a Higgs-like particle with an energy of around 126 GeV.

Yet while the Higgs looks like that predicted by the Standard Model of particle physics, further measurements were needed before researchers could be sure.

The Higgs decays into other particles in a number of ways, but Hill reports that the so-called “diphoton channel” – where the Higgs decays into two photons – is still higher than that predicted by the Standard Model. This is shown in both the  ATLAS and CMS experiments. Every other decay agrees well with Standard Model predictions.

Fermilab physicist Joseph Lykken adds that this excess could be evidence that supersymmetric particles are involved in the decay.

Not only that but the Higgs’s spin state has yet to be pinned down. A Standard Model Higgs is expected to have a spin state of zero but the LHC has not yet enough data to determine that.

“There is strong evidence to favour the scalar spin zero,” says Hill who works on the CMS experiment at the LHC. “But spin two cannot be ruled out yet so it is not conclusive”.

So more data crunching is needed and with the LHC shutdown until 2015 to undergo a series of upgrades at least scientists at the LHC will have time to do that.

As Lykken adds, “the ball is now in the theorists court”.