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Science

Lepton Universality In Question, a Standard Model Assumption 62

Posted by Soulskill
from the we'ere-slightly-more-wrong-than-we-thought dept.
Charliemopps writes: "Over the past few years, more and more experiments have started to question one of the core assumptions of the standard model: Lepton Universality. Simply put, the weak nuclear force is assumed to work equally on all Leptons (electron, muon and tau). Two years ago The Babar experimental collaboration reported that measurements indicated this may not have been the case. But the measurements were not accurate enough to be definitive.

Now, a report from The LHC shows that they have analyzed their entire dataset of proton-proton collisions and found a rather large discrepancy. These measurements are still not all that accurate. These decays happen so rarely that even with this huge data set there is still about a 1% change they are incorrect. One explanation for such measurements is an as-yet-undiscovered, charged Higgs particle. It would have to be extremely heavy: greater than 109GeV possibly even as high as 150GeV. This is predicted by some models outside of the Standard Model, like Supersymmetry."
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Lepton Universality In Question, a Standard Model Assumption

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  • But... (Score:5, Informative)

    by Stormy Dragon (800799) on Wednesday June 04, 2014 @06:24PM (#47167833) Homepage

    This is predicted by some models outside of the Standard Model, like Supersymmetry.

    Except that that LHC's ongoing failure to find any SUSY particles is making it increasingly unlikely Supersymmetry is right either:

    http://scienceblogs.com/starts... [scienceblogs.com]

  • Re:But... (Score:5, Informative)

    by jfengel (409917) on Wednesday June 04, 2014 @06:49PM (#47167935) Homepage Journal

    The data go a long way to ruling out the Minimal Supersymetric Standard Model (MSSM), but other SUSY theories are still in the running. The MSSM has the advantage of being, well, minimal, but there's no special reason to expect the universe to have made it that easy on us.

    It's hard to say which theory this points us to, if any, but the Two Higgs Doublet Model (2HDM) is a part of several. Those theories will help refine what kind of data to look for and what kinds of experiments to configure.

  • Re:How convenient! (Score:4, Informative)

    by cjameshuff (624879) on Wednesday June 04, 2014 @07:21PM (#47168143) Homepage

    Consider how long it took to gather enough of the right events to be reasonably certain about the Higgs, the various false alarms that vanished as more data was collected, etc. Another version just a bit rarer could easily be lost in the noise. Or the two could be similar enough that their signals aren't distinguishable from each other yet.

  • by ceoyoyo (59147) on Wednesday June 04, 2014 @09:41PM (#47168787)

    The standard model is an extremely comprehensive collection of theories that makes incredibly accurate predictions. It's a crappy computational tool. It's so computationally intractable that it requires supercomputers to simulate even simple multi-particle systems.

To downgrade the human mind is bad theology. - C. K. Chesterton

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