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LHCb results show generation non-Universality (non-SM)

  1. Aug 31, 2015 #1

    ChrisVer

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    This article suggests something was found and that today we will be able to find the paper online.
    http://www.eurekalert.org/pub_releases/2015-08/uom-ess082615.php

    I am eager to see what the found and at what significance....asking for extra experiments means that the significance they got was not high enough to consist an actual discovery(?). So nevertheless if someone sees the publication before I do, post it here please?

    Nevertheless it would be cool... either for SUSYs (non-minimal coupling) or GUTs (like a NUGIM I guess)... although it's getting quiet tiring with the news they let to reach out the world (with a significance of >2std we are told that something new was discovered...I guess that's marketing)
     
  2. jcsd
  3. Aug 31, 2015 #2
    Hey, Chris,
    This is probably the arXiv version of the paper-
    http://arxiv.org/abs/1506.08614

    Still not online at PRL

    Measurement of the ratio of branching fractions B(B¯¯¯0→D∗+τ−ν¯τ))/B(B¯¯¯0→D∗+μ−ν¯μ)


    Abstract-
    The branching fraction ratio R(D∗)≡B(B¯¯¯0→D∗+τ−ν¯τ)/B(B¯¯¯0→D∗+μ−ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0\invfb of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ−→μ−ν¯μντ. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯¯¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). 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.
     
  4. Aug 31, 2015 #3

    ChrisVer

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    I also checked that but I was told (and later figured out by myself) that it was old (late June and not ends of August).
     
  5. Aug 31, 2015 #4

    mfb

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    Looks like a false alarm.

    LHCb publishes important results on their public page before random news websites get them. Nothing there. Also, CERN would make a press release.

    eurekalert.org refers to Brian Hamilton as one of the leading analyzers, which matches the arXiv preprint websterling found, and the description fits as well. It is also in agreement with a different recent news directly linking this (and mentioning the same publication date).
    2.1 sigma significance is nothing. There are multiple 2-sigma-deviations, but those measurements are not independent.
     
  6. Aug 31, 2015 #5
    Last edited: Aug 31, 2015
  7. Aug 31, 2015 #6

    mfb

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    Right, but 2.1 sigma is not a significant result. Although some "scientific" disciplines believe it would be.
    The 3.9 sigma combination is mainly driven by BaBar analyses 2012 and 2013.
    For sure.
    Add ##H \to \mu \tau## to the list, although it is hard (but not impossible) to get that without violating muon decay constraints.
     
  8. Sep 16, 2015 #7
    It's hard to say anything right now with 2.1 sigma, I would suggest let's just wait and see when more data come out.
     
  9. Sep 17, 2015 #8

    ChrisVer

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    And is that good or bad?o_O
     
  10. Sep 17, 2015 #9

    mfb

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    It means the LHCb result is not contributing very much to the average.
    2016 data should help, and by 2018 LHCb might be much more precise than the other experiments if the systematics can be reduced sufficiently.
     
  11. Sep 17, 2015 #10
  12. Sep 17, 2015 #11

    mfb

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    And multiple other measurements with a ~2 sigma tension all in the same direction, but those have correlated systematics so they could have a common source.
    Run 2 of the LHC will certainly be interesting.
     
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