August 07, 2016

"A specific hypothesis about gravitons (hypothetical force-carriers for gravity) suggest that they could decay through a process that produces two high-energy photons."

ars technica: The teams behind the ATLAS and CMS detectors searched their data for collisions that produced two photons and then compared their numbers to predictions of what they should see based on the Standard Model. by John Timmer

'That analysis turned up an apparent excess at an energy of 750 Giga-electronVolts. While the excess showed up in data from both detectors, it didn't reach levels significant enough to call it a discovery. Under these circumstances, all physicists can do is wait for more data. Fortunately, the LHC has been delivering data at a phenomenal pace.

'The entire 2015 high-energy run produced just under four inverse-femtobarns (don't ask, it's just what physicists use) of data. Now, with only part of the data from this year's run, they were able to add another 12.9 inverse femtobarns to the analysis. And, with this new data, the bump in the earlier analysis went away. "No significant excess is observed over the Standard Model predictions," according to a summary put out by the CMS detector team.

'As a result of this analysis, the LHC team is able to put hard limits on the possible masses of this type of graviton (they probably don't exist below four Tera-electronVolts). This doesn't mean that gravitons don't exist—there are other theoretical types—just that we can't find evidence of these particular gravitons.'

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