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A Dark matter does not contain certain axion-like particles

  1. Aug 9, 2016 #1
    this was widely reported in the past, but not commented on

    here
    https://www.sciencedaily.com/releases/2016/04/160422115320.htm

    based on
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.161101

    Search for Spectral Irregularities due to Photon–Axionlike-Particle Oscillations with the Fermi Large Area Telescope
    M. Ajello et al. (The Fermi-LAT Collaboration)
    Phys. Rev. Lett. 116, 161101 – Published 20 April 2016


    Abstract
    We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5×10−12GeV−1 for ALP masses 0.5≲ma≲5neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe.



    how strong are those bounds, how good are those results?

    note they only pertain to axions as stable cold dark matter. axions could exist but are unstable and decay.

    so cold dark matter hypothesis just in 2016

    axion and axion-like particles ruled out by astrophysical observations

    sterile neutrinos ruled out by ice cube

    WIMPS large parameter space ruled out by LUX and PandaX

    SUSY-WIMPS large parameter space ruled out by LUX and PandaX

    WIMPS not produced nor detected by Large Hadron Collider


    anything else?
     
  2. jcsd
  3. Aug 10, 2016 #2

    ohwilleke

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    Gold Member

    Not too surprising. Generally speaking, only electromagnetically charged particles should have interactions with photons. This conclusions should impact any version of an axions that lacks electrical charge. (There could be higher order loops that create particle-antiparticle pairs with electric charge that interact, I suppose, but those would be highly suppressed relative to tree level interactions with axions.)
     
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