Dec 14 2012
Scientists searching for the Higgs boson on the ATLAS experiment at the Large Hadron Collider near Geneva are reporting small discrepancies from the two main channels they use to look for the particle.
A stuffed animal artist’s conception of the Higgs boson.
With these channels – the decay of a Higgs to two light particles (photons) or to two Z bosons – the scientists determined the mass of the Higgs-like particle to be roughly 125 GeV, about 125 times the mass of the proton.
They announced complimentary results from both channels in July 2012, and since then have been crunching more data to support the findings. The scientists gave updates on their work Dec. 13 at CERN.
“It’s turned out that for ATLAS the Zed-Zed channel and gamma-gamma channel differ quite a bit, by about 3 GeV, for the respective masses of the Higgs particle from which they decay,” says Duke physicist Mark Kruse, who is analyzing data from the ATLAS experiment. “It doesn’t sound like much, but the probability they could differ by this much or more is only about 0.5 percent.”
“This is probably not a big deal,” he says, noting that the new results explain why the ATLAS team was not ready to report the separate mass measurements at the November 2012 Hadron Collider Physics Symposium in Kyoto, Japan.
Kruse says there could be several reasons for the discrepancy. It could just be a statistical fluke. Or, there could be a subtle problem with one or both of the measurements. “There is a lot that goes into these analyses and it is not always possible at this stage to be absolutely certain every detail has been done perfectly,” Kruse says.
The more dramatic scenario is that these results could be due to two different Higgs-like particles.
Kruse, however, thinks the two Higgs-like particle answer is highly unlikely, especially if scientists using the CMS experiment at LHC do not report the same discrepancy. CMS scientists have not yet released their new “two photon” result.
The ATLAS result is most likely due to a statistical fluctuation. Right now, though, the team has only crunched about half the data from the collisions. Of course, scientists will only know more once they have analyzed the full ATLAS dataset a couple of months from now, Kruse adds, suggesting that there is still the possibly for more Higgs mania to come.