Subatomic particles that appear to defy Standard Model

Re:Subatomic particles that appear to defy Standard Model by tobias2014 on Sunday August 30, 2015 @09:11AM (#10143199)

Is it this paper they are talking about? http://inspirehep.net/record/1380182

"This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the Standard Model."

To see how much this is relevant see for example http://blogs.scientificamerican.com/observations/five-sigmaw...

Usually physicists claim "evidence" for something at 3 standard deviations and "discovery" at 5 standard deviations.

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Re:Subatomic particles that appear to defy Standard Model by nitrogen on Sunday August 30, 2015 @03:18PM (#10144216)

I think you may be conflating deviation from expectation, which is just a percentage dependent on the width of the distribution, with statistical significance. An experiment with 5 std. dev. significance[0][1] could still confirm a value that is 2.1 std. dev. above the center of the range[2] that was originally predicted.

Corrections welcome.

[0] https://en.wikipedia.org/wiki/Standard_deviation#Experiment.... [1] https://en.wikipedia.org/wiki/Statistical_significance#Strin... [2] https://en.wikipedia.org/wiki/Standard_deviation#/media/File...

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Re:Subatomic particles that appear to defy Standard Model by grkvlt on Monday August 31, 2015 @03:50AM (#10145896)

No, he is right. In particle physics standard deviation from the normal distribution of results is used to show that a result is significant and new (i.e. a previously unknown partcle) rather than just random noise.[1][2] The 'sigma' notation is then used to show how many standard deviations away the result is, such as in the Higgs discobery, when a '5 sigma' standard was used to confirm discovery. [3]

The references linked probably explain this a lot better than I have.

    [1] http://blogs.scientificamerican.com/observations/five-sigmawhats-that/
    [2] http://physics.stackexchange.com/questions/8752/standard-deviation-in-particle-physics
    [3] http://understandinguncertainty.org/explaining-5-sigma-higgs-how-well-did-they-do

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Re:Subatomic particles that appear to defy Standard Model by buovjaga on Sunday August 30, 2015 @10:38AM (#10143428)

Yes, you found the right paper, it is mentioned here: https://cmns.umd.edu/news-events/features/3188

"The research paper, “Measurement of the ratio of branching fractions...,” The LHCb Collaboration, is scheduled to appear online August 31, 2015 and to be published September 4, 2015 in the journal Physical Review Letters."

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