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The Two-Photon Excess at LHC Brightens Slightly

18 Mar 2016, 12:29 UTC
The Two-Photon Excess at LHC Brightens Slightly
(200 words excerpt, click title or image to see full post)

Back in December 2015, there was some excitement when the experiments ATLAS and CMS at the Large Hadron Collider [LHC] — especially ATLAS — reported signs of an unexpectedly large number of proton-proton collisions in which

two highly energetic photons [particles of light] were produced, and
the two photons could possibly have been produced in a decay of an unknown particle, whose mass would be about six times the mass of the Higgs particle (which ATLAS and CMS discovered in 2012.)

This suggested the possibility of an unknown particle of some type with rest mass of 750 GeV/c². However, the excess could just be a statistical fluke, of no scientific importance and destined to vanish with more data.
The outlook for that bump on a plot at 750 GeV has gotten a tad brighter… because not only do we have ATLAS’s plot, we now have increasing evidence for a similar bump on CMS’s plot. This is thanks largely to some hard work on the part of the CMS experimenters. Some significant improvements at CMS,

improved understanding of their photon energy measurements in their 2015 data,
ability to use 2015 collisions taken when their giant magnet wasn’t working — fortunately, the ...

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