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Thread: Searching for Dark Matter

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    Administrator lpetrich's Avatar
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    Searching for Dark Matter

    Dark Matter is the name given to a mysterious substance that contributes much of the Universe's mass. Strictly speaking, it is not "dark" but invisible. The only evidence that we have of its existence is from its gravity -- we have yet to discover any convincing nongravitational evidence of its existence.

    4 Dark Matter Experiments to Keep an Eye on in 2019
    LIGO comes back online
    Can LIGO Find the Missing Dark Matter?
    It might be primordial black holes, and LIGO might detect g-wave evidence of them.

    Physicists will try to figure out whether MiniBooNE gave up the ghost of a neutrino
    Possible evidence of "sterile neutrinos" in its data.

    First light at the Large Synoptic Survey Telescope (LSST)
    There's a telescope being built in Chile that will make detailed images of vast regions of the sky every 15 seconds, completing a full scan of the sky every three days. Over the course of 10 years, it will compare those images to one another again and again to track how the sky shifts and changes, providing the most in-depth-ever resource for understanding how dark matter pushes and pulls on the cosmos.
    The race to build a next-generation detector will heat up
    Particle physicists have speculated for a long time that the first direct sign of dark matter might be a sparkle. Here's how it might work: As dark matter collides with inert substances in very dark rooms, those substances would emit faint specks of light. For decades, scientists have built detectors according to this principle, but so far, none have produced a conclusive result.
    Not just sparkles of light, but "sparkles" of sound, from dark-matter particles bouncing off of detector-material atomic nuclei.

    Three experiments are being worked on, each of which will look at 4 to 10 tons of xenon. They should start operation this year or the next.

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    Contributor repoman's Avatar
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    So, is there really a Planck energy for a particle at which it basically will be its own black hole?

    https://en.wikipedia.org/wiki/Planck_energy

    So, even the Oh My God particle was somewhere on the order of 2.5×10−8 Planck Energy and this article says that the LHC is 10^-15 times as energetic per particle than the Planck Energy.

    https://www.scientificamerican.com/a...holes-2007-04/

    Could it be that Dark Matter and Baryonic Matter can only inter-convert at appreciable rates at say 10-4 Planck Energy?

    This is just spitballing, of course.

    But that may explain why Dark Matter is inert now.

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    Administrator lpetrich's Avatar
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    Review of Direct Dark-Matter Searches

    A new elementary particle? It would be a Weakly Interacting Massive Particle, a WIMP.

    Supersymmetry neutralino? Gravitino? Axion? Sterile neutrino? Something else?

    WIMP's would be relics of the early Universe, produced when the Universe was hot enough to do so. Temperature ~ energy ~ mass*c^2.

    How to make them?
    • The LHC: protons -> WIMP's + a lot of other stuff
    • Indirect: WIMP + WIMP -> familiar particles
    • Direct: WIMP + nucleus -> WiMP + kicked nucleus


    We are in our galaxy's dark-matter halo, and our orbit in our galaxy will make a dark-matter "wind". Our orbit around the Sun will make a modulation of that wind: 30 km/s out of 220 km/s.

    Need to reduce background events. To avoid cosmic rays, one must go deep underground. One must also try to remove radioactive isotopes of materials in the detectors. The ultimate background will be neutrinos, but we are still some way off from observing those particles. But upcoming experiments are getting closer and closer.

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    Contributor repoman's Avatar
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    For the modeling of the early universe, there was the point when neutrinos decoupled from matter and now those neutrinos are not detectable due to cosmological redshifting except maybe in insanely subtle ways that also are affected by other processes. There was a thread on this a couple months ago.

    Is it possible that if dark matter is made of elementary particle(s) that these also decoupled early on and are similarly redshifted and nearly undetectable? Of course it is the tiny mass of the neutrinos that allowed the high level of redshifting.

    But even all the relic neutrino mass is not much, could these dark matter elementary particles add up to the missing mass and not totally mangle the big bang model?

    This looks interesting

    https://arxiv.org/abs/1706.06801

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