Could we have already discovered dark matter?
That's the question put forth in a new paper published Feb.12 in the Journal of Physics G. The authors outlined how dark matter might be made of a particle known as the d*(2380) hexaquark, which was likely detected in 2014.
Dark matter, which exerts gravitational pull but emits no light, isn't something anyone's ever touched or seen. We don't know what it's made of, and countless searches for the stuff have come up empty. But an overwhelming majority of physicists are convinced it exists. The evidence is plastered all over the universe: Clusters of stars spinning far faster than they otherwise should, mysterious distortions of light across the night sky, and even holes punched in our galaxy by an unseen impactor point to something being out there — making up most of the mass of the universe — that we don't yet understand.
Most widely studied theories of dark matter involve whole classes of never-before-seen particles from well outside the Standard Model of physics, the dominant theory describing subatomic particles. Most of these fit into one of two categories: the lightweight axions and the heavyweight WIMPs, or weakly interacting massive particles. There are other, more exotic theories involving as-yet undiscovered species of neutrinos or a theoretical class of microscopic black holes. But rarely does anyone propose that dark matter is made of something we already know exists.
Mikhail Bashkanov and Daniel Watts, physicists at the University of York in England, broke that mold, arguing that the d*(2380) hexaquark, or "d-star," could explain all the missing matter.
Quarks are fundamental physical particles in the Standard Model. Three of them bound together (using particles known as gluons) can make a proton or a neutron, the building blocks of atoms. Arrange them in other ways and you get different, more exotic particles. The d-star is a positively charged, six-quark particle that researchers believe existed for a sliver of a second during a 2014 experiment at Germany's Jülich Research Center. Because it was so fleeting, that d-star detection hasn't been absolutely confirmed.
Individual d-stars couldn't explain dark matter because they don't last long enough before decaying. However, Bashkanov told Live Science, early in the universe's history, the particles might have clumped together in a way that would have kept them from decaying.
That scenario occurs with neutrons. Take a neutron out of a nucleus, and it very quickly decays, but mix it with other neutrons and protons inside the nucleus, and it becomes stable, Bashkanov said.
"Hexaquarks behave in exactly the same way," Bashkanov said.
Bashkanov and Watts theorized that groups of d-stars could form substances known as Bose-Einstein condensates, or BECs. In quantum experiments, BECs form when temperatures drop so low that atoms begin to overlap and blend together, a bit like the protons and neutrons inside atoms. It's a state of matter distinct from solid matter.
Early in the universe's history, those BECs would have captured free electrons, forming a neutrally charged material. A neutrally charged d-star BEC, the physicists wrote, would behave a lot like dark matter: invisible, slipping through luminous matter without noticeably bumping it around, yet exerting significant gravitational pull on the surrounding universe.
The reason you don't fall through a chair when you sit on it is that the electrons of the chair push against the electrons of your backside, creating a barrier of negative electric charges that refuse to cross paths. Under the right conditions, Bashkanov said, BECs made of hexaquarks with trapped electrons would have no such barriers, slipping through other kinds of matter like perfectly neutral ghosts.
These BECs might have formed soon after the Big Bang, as space transitioned from a sea of hot quark-gluon plasma with no distinct atomic particles into our modern era with particles like protons, neutrons and their cousins. At the moment when those basic atomic particles formed, conditions were perfect for hexaquark BECs to precipitate from the quark-gluon plasma.
"Before this transition, the temperature is too high; after it, the density is too low," Bashkanov said.
During this transition period, the quarks could have frozen into either ordinary particles, such as protons and neutrons, or into the hexaquark BECs that today might make up dark matter, Bashkanov said. If these hexaquarks BECs are out there, the researchers wrote, we might be able to detect them. Even though the BECs are quite long-lived, they will occasionally decay around Earth. And that decay would show up as a particular signature in detectors designed to spot cosmic rays, and appear as if it were coming from every direction at once as if the source filled all of space.
The next step, they wrote, is to look for that signature.
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Originally published on Live Science.
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I say this respectfully, and without any measure of snark, but I'll believe it when I see it. What would the decay signature look like, and how might we detect it with the instrumentation that we have in place today?admin said:A new theory suggests that dark matter might not be made of undiscovered, never-before-seen particles. Instead, researchers write, it might be made from a type of "hexaquark" detected in 2014.
Did German physicists accidentally discover dark matter in 2014? : Read more
Wouldn't this mean that cosmic inflation would kick in just after this brief epoch (is that a buzz word?) of star formation when these condensates begin to evaporate from photon absorption?Reply
admin said:A new theory suggests that dark matter might not be made of undiscovered, never-before-seen particles. Instead, researchers write, it might be made from a type of "hexaquark" detected in 2014.
Did German physicists accidentally discover dark matter in 2014? : Read more
Seems to me their toy model BEC condensate is merely targeted to produce primordial gaseous mass. They claim that the condensates would make massive atom analog "nuclei", which would be charge neutral analogous to atoms by forming surrounding electron clouds. "The upper d*(2380)-BEC multiplicity limits (for the assumed attractive d*−d* interaction) correspond to masses at the gram scale. Such d*(2380)-BEC ‘nuclei’ would posses a very large positive charge."
However, if that is the case, it fails the cosmological dark matter characteristics of not interacting with electromagnetism and of not coupling to light so primordial baryonic acoustic oscillations can appear.
They also don't discuss the condensate stability at the temperatures of the cosmic background radiation - which it seems to couple with - or other heating.
This toy model doesn't seem to go very far.
kamikrazee said:I say this respectfully, and without any measure of snark, but I'll believe it when I see it. What would the decay signature look like, and how might we detect it with the instrumentation that we have in place today?
It should be "easy" -- accelerator experiments: you should see a resonance, at 2380 MeV, that is 70MeV wide, and has I(J^P) of 3(0^+) which is already seen and measured, here: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.202301 I suppose that confirmation is now sorely needed.
I'm really annoyed that this article is mis-titled: which German lab? What did they see in 2014? Is it this resonance? Something else? Or are they referring to this PRL? Not clear.
TorbjornLarsson said:" Such d*(2380)-BEC ‘nuclei’ would posses a very large positive charge."
However, if that is the case, it fails the cosmological dark matter characteristics of not interacting with electromagnetism and of not coupling to light
Completely unclear to me is the electronic structure of the thing. They propose two nuclear shapes: a sphere and a linear chain, suggesting the chain is more likely. What's the binding energy of the most loosely bound electron? If its a few eV, then yes, you've got a serious problem with coupling to light. If its a few keV or MeV, then in practice , it will not be ionized, it's effectively non-interacting with stellar light, cosmic background.
Bradley Busch said:Wouldn't this mean that cosmic inflation would kick in just after this brief epoch (is that a buzz word?) of star formation when these condensates begin to evaporate from photon absorption?
I think the term is eon, and the Inflation Eon is the eon that comes before all the others.
Short explanation here: P1Q8tS-9hYoView: https://www.youtube.com/watch?v=P1Q8tS-9hYo
Physics of inflation here:
linas said:Completely unclear to me is the electronic structure of the thing. They propose two nuclear shapes: a sphere and a linear chain, suggesting the chain is more likely. What's the binding energy of the most loosely bound electron? If its a few eV, then yes, you've got a serious problem with coupling to light. If its a few keV or MeV, then in practice , it will not be ionized, it's effectively non-interacting with stellar light, cosmic background.
During the radiation dominated expansion baryons was observably coupled to light at relativistic speeds while dark matter was not. Are you suggesting that somehow a coupling to light would not become relativistic at those pressures and temperatures?
linas said:I'm really annoyed that this article is mis-titled: which German lab? What did they see in 2014? Is it this resonance? Something else? Or are they referring to this PRL? Not clear.
Maybe they refer to the 2014 experimental reference? https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.202301 : "The experiment was carried out with the WASA detector setup at COSY ...".
Thanks for having me dig into this, I studied at the old Ångström locales and the short circuit bangs from the basement tandem accelerator was a weekly shakeup. I did not know that some detectors like WASA ended up at COSY in Germany http://collaborations.fz-juelich.de/ikp/wasa/ ]:
"WASA (Wide Angle Shower Apparatus) is a large-acceptance detector for charged and neutral particles. It has been operated at the CELSIUS storage ring at The Svedberg Laboratory in Uppsala (Sweden) until June 2005. After the shutdown of CELSIUS the detector setup was relocated to continue its operation at the Cooler Synchrotron COSY in Jülich. It was installed in summer 2006 and has successfully taken data until middle of 2014. In 2015 the central detector together with the pellet target had been removed and the target area has been refurbished in order to use the forward detector as azimuthally symmetric polarimeter for the EDM at COSY. "
I realize that I may be in the minority, but I still have a hard time believing that dark matter even exists. The failure to find any at the center of the Milky Way is one piece of evidence that has not been sufficiently explained away.Reply
Instead, I still think there is a possibility that our calculations about inflation and measurements are being affected by some as yet unknown effect, whether that turns out to be errors in relativity theory, an effect resulting from Dark Flow, or even that Newton's formula varies with distance. There are many other possibilities and it will be interesting to see how this plays out. Loop Quantum Gravity may be closer, in general, to an explanation than M-Theory.
Live science discovers dark matter once a week. Yawn...Reply