Higgs Hiccup: Contradictory Results Show Up at LHC
By Adam Mann, Wired
12.14.12 2:08 PM
Ever since physicists found a particle that looks very much like the Higgs boson in July, they have been probing its properties, essentially running their experimental hands all over it to check out its features. They do this by smashing protons together at insanely high speeds in the Large Hadron Collider and watching the resulting rain of particles that gets produced. Within this melee, several Higgs bosons appear and almost immediately decay into other particles.
The LHC can detect the Higgs decaying in two different ways. One channel produces two characteristic photons while another creates four particles known as leptons. The two decay paths each give scientists a distinct value for the mass of the Higgs. But there’s a little problem.
“There turns out to be a slight tension between the two masses,” said physicist Beate Heinemann of the University of California, Berkeley, who works on ATLAS, one of the LHC’s Higgs-searching experiments. “They are compatible, just not super compatible.”
The two photon channel is saying that the Higgs mass is 126.6 gigaelectronvolts (GeV), or about 126 times the mass of a proton. The four lepton decay route suggests the mass is 123.5 GeV. A very tiny disagreement that is nonetheless very strange because the Higgs should have one identifiable mass. ATLAS scientists noticed the discrepancy in their data previously and thought it might simply be a problem with calibrating their machinery. Yet even after calibration and analyzing more data, the difference remained.
We looked for one. We may have found two.
Vasudevan Mukunth, The Hindu
December 15, 2012
There was initial surprise in Kyoto about the dilepton-decay data being suppressed. However, the experimental data of the Higgs’ decay into the other combinations of particles coincided (fairly) perfectly with the theoretical predictions, easing physicists toward the conclusion that the Standard Model had done a good job… again.
And now, the reason for suppression has been revealed! On December 13 (exactly a year to the day the first tentative spottings were announced), a new round of data from the ATLAS detector was revealed at CERN, showing that the Higgs boson seemed to be decaying into two photons twice as often as allowed by the Standard Model. Not just that: the elusive particle also seemed to exist at two different masses – almost as if there are two kinds of Higgs bosons, not one.
The “second mass” observation was derived from results of the particle’s decay into four leptons. More specifically, at 4.1 standard-deviations (a confidence level of 99.534 per cent), the mass of the Higgs boson from this channel was calculated to be 123.5 +/- 0.9 GeV, which is conspicuously lower than the mass observed from the diphoton-decay channel (by about 3 GeV).
Before we start jumping up and down: The ATLAS collaboration has also announced that the two masses are compatible only at 2.7 standard deviations, which represents a lower statistical confidence than is required to assert evidence. Moreover, results from the CMS collaboration will also have to be factored in before anything is confirmed, and the next batch of data-release from CERN is expected in March, 2013. And last, it’s quite unlikely that the Higgs would have a twin so close in mass – if you’ve already walked 122.6 m, would you consider another 3 m as requiring a lot more energy than what you’ve already spent?
But, if true, this result invalidates the ‘Standard Model‘. Brains.
Why a Zombie Movie Made by Physicists is the Best Kind of Science PR
By J. Bryan Lowder, Slate
Wednesday, Dec. 12, 2012, at 2:15 PM ET
Decay is totally ridiculous, in the best sense of the word. The 75-min, $3,500 movie is remarkably well-made, given the creative team’s lack of experience. It’s studded with all the gratuitous gore, cheap shocks, and absurd plot twists that zombie fans crave. Science nerds and those who love them will bask in its shameless use of sci-fi clichés like “the results are inconclusive at best,” and “my research is too important!”