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Exciting Day Ahead at LHC

15 Dec 2015, 12:45 UTC
Exciting Day Ahead at LHC
(200 words excerpt, click title or image to see full post)

At CERN, the laboratory that hosts the Large Hadron Collider [LHC]. Four years ago, almost to the day. Fabiola Gianotti, spokesperson for the ATLAS experiment, delivered the first talk in a presentation on 2011 LHC data. Speaking to the assembled scientists and dignitaries, she presented the message that energized the physics community: a little bump had shown up on a plot. On the plot were the numbers of proton-proton collisions that had produced two energetic photons (particles of light), shown versus the “invariant mass” of the two photons (the mass that a parent particle would have had, if the two photons had come from a parent particle — although the vast majority of them do not.) Most two-photon production processes are pretty random, and produce data that forms a smooth curve on such a plot. But a new particle decaying to two photons would, if it existed, be observed as a little upward wiggle on that curve. And that’s what ATLAS’s data showed.
ATLAS’s two-photon data in Dec. 2011. The data are the black dots; the red line is there to guide the eye and show you that the data is smooth… except for a curious little bump at around ...

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