New theory of stealth dark matter may explain universe’s missing mass

Oct 2, 2015

DOE/Lawrence Livermore National Laboratory

By DOE/Lawrence Livermore National Laboratory

Lawrence Livermore scientists have come up with a new theory that may identify why dark matter has evaded direct detection in Earth-based experiments.

A group of national particle physicists known as the Lattice Strong Dynamics Collaboration, led by a Lawrence Livermore National Laboratory team, has combined theoretical and computational physics techniques and used the Laboratory’s massively parallel 2-petaflop Vulcan supercomputer to devise a new model of dark matter. It identifies it as naturally “stealthy” (i.e. like its namesake aircraft, difficult to detect) today, but would have been easy to see via interactions with ordinary matter in the extremely high-temperature plasma conditions that pervaded the early universe.

“These interactions in the early universe are important because ordinary and dark matter abundances today are strikingly similar in size, suggesting this occurred because of a balancing act performed between the two before the universe cooled,” said Pavlos Vranas of LLNL, and one of the authors of the paper, “Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability.” The paper appears in an upcoming edition of the journalPhysical Review Letters and is an “Editor’s Choice.”


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3 comments on “New theory of stealth dark matter may explain universe’s missing mass

  • I wish when journalists write this many words about something they’d at least summarise it well. As always, the original study does a better job with its abstract. If you know how baryons are composed of quarks, you’ll understand the idea in this model, which is that dark matter is composed of analogous particles with some even number of quark equivalents inside.



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  • I sometimes have this thing where I think I’m understanding something as I read or hear it, then it kind of evaporates from my head after a few minutes. This article caused that thing to happen to me. It also happened in “The 4 Universe” when they explained how cosmic expansion is justified mathematically.

    What I don;t get HERE is: how would the possibility of new types of stealth ‘quarks’ make it so the stealth matter doesn’t interact except through gravity?



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  • 3
    Peter Clemerson says:

    To Jos Gibbons. I can’t agree with your comment about the abstract. Here it is.
    “We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar baryon dark matter candidate — “Stealth Dark Matter”, that is based on a dark SU(4) confining gauge theory. In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest baryons in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure, however the steep dependence on the dark matter mass, 1/m6B, suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter. ”

    Who but a specialist would understand more than the first few words?



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