ATLAS Results: One Higgs Or Two? 73
TaeKwonDood writes with news from CERN about more results in the search for the Higgs Boson, this time from the ATLAS experiment. Researchers report peaks in the data in accordance with what they'd expect from the Higgs. The curiosity is that the peaks are a couple GeV away from each other. "The ATLAS analyses in these channels return the best fit Higgs masses that differ by more than 3 GeV: 123.5 GeV for ZZ and 126.6 GeV for gamma-gamma, which is much more than the estimated resolution of about 1 GeV. The tension between these 2 results is estimated to be 2.7sigma. Apparently, ATLAS used this last month to search for the systematic errors that might be responsible for the discrepancy but, having found nothing, they decided to go public." Scientific American has a more layman-friendly explanation available. As this work undergoes review, physicists hope more eyes and more data will shed some light on this incongruity. Tommaso Dorigo, a particle physicist working at the CMS experiment at CERN, writes, "Another idea is that the gamma-gamma signal contains some unexpected background which somehow shifts the best-fit mass to higher values, also contributing to the anomalously high signal rate. However, this also does not hold much water — if you look at the various mass histograms produced by ATLAS (there is a bunch here) you do not see anything striking as suspicious in the background distributions. Then there is the possibility of a statistical fluctuation. I think this is the most likely explanation." Matt Strassler provides a broader update to the work proceeding on nailing down the Higgs boson.
Gods' particles (Score:2, Informative)
I fixed the title for you.
Probably chance (Score:5, Informative)
2.7 sigma isn't actually that much: assuming a Gaussian distribution of data, it's a one-in-a-hundred chance of being randomness rather than a real difference (or in other terms, about one experiment in a hundred will generate a false signal). For comparison, the standard for announcing a new particle is 5 sigma (1 in 1.7 million chance of it being a false positive).
Re:The most wonderful exclamation in science (Score:5, Informative)
The collider beams go off by a few millimetres. Oceans go up and down by as much as several meters.
http://science.slashdot.org/story/12/06/08/222247/how-the-moon-affects-lhc-operations [slashdot.org]
http://www.quantumdiaries.org/2012/06/07/is-the-moon-full-just-ask-the-lhc-operators/ [quantumdiaries.org]
http://www.lhup.edu/~dsimanek/scenario/tides.htm [lhup.edu]
The "tidal trivia" summary below puts things into perspective. The so-called equatorial bulge due to the Earth's axial rotation lifts the equator about 23 kilometer. The moon's gravity gradient lifts water mid-ocean (where the ocean is deep) no more than 1 meter, that's 1.6 x 10-7% of the Earth radius. Why do we fuss about this? Because over an ocean of large area, that represents a very large volume of water. Also, it's the driving mechanism that controls the periods of the much larger tides at shorelines.