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posted by janrinok on Wednesday September 11 2019, @04:52PM   Printer-friendly
from the we-like-near-misses dept.

Arthur T Knackerbracket has found the following story:

New findings from University of Kansas experimental nuclear physicists Daniel Tapia Takaki and Aleksandr (Sasha) Bylinkin were just published in the European Physical Journal C. The paper centers on work at the Compact Muon Solenoid, an experiment at the Large Hadron Collider, to better understand the behavior of gluons.

Gluons are elementary particles that are responsible for "gluing" together quarks and anti-quarks to form protons and neutrons—so, gluons play a role in about 98% of all the visible matter in the universe. Previous experiments at the now-decommissioned HERA electron-proton collider found when protons are accelerated close to light-speed, the density of gluons inside them increases very rapidly.

"In these cases, gluons split into pairs of gluons with lower energies, and such gluons split themselves subsequently, and so forth," said Tapia Takaki, KU associate professor of physics & astronomy. "At some point, the splitting of gluons inside the proton reaches a limit at which the multiplication of gluons ceases to increase. Such a state is known as the 'color glass condensate,' a hypothesized phase of matter that is thought to exist in very high-energy protons and as well as in heavy nuclei."

The KU researcher said his team's more recent experimental results at the Relativistic Heavy Ion Collider and LHC seemed to confirm the existence of such a gluon-dominated state. The exact conditions and the precise energy needed to observe "gluon saturation" in the proton or in heavy nuclei are not yet known, he said.

"The CMS experimental results are very exciting, giving new information about the gluon dynamics in the proton," said Victor Goncalves, professor of physics at Federal University of Pelotas in Brazil, who was working at KU under a Brazil-U.S. Professorship given jointly by the Sociedade Brasileira de Física and the American Physical Society. "The data tell us what the energy and dipole sizes are needed to get deeper into the gluonic-dominated regime where nonlinear QCD effects become dominant."

Although experiments at the LHC don't directly study interaction of the proton with elementary particles such as those of the late HERA collider, it's possible to use an alternative method to study gluon saturation. When accelerated protons (or ions) miss each other, photon interactions occur with the proton (or the ion). These near misses are called ultra-peripheral collisions (UPCs) as the photon interactions mostly occur when the colliding particles are significantly separated from each other.

[...] The researchers said the work is significant because it's the first establishment of four measured points in terms of the energy of the photon-proton interaction and as a function of the momentum transfer.

"Previous experiments at HERA only had one single point in energy," Tapia Takaki said. "For our recent result, the lowest point in energy is about 35 GeV and the highest one is about 180 GeV. This does not sound like a very high energy point, considering that for recent J/psi and Upsilon measurements from UPCs at the LHC we have studied processes up to the 1000s GeV. The key point here is that although the energy is much lower in our Rho0 studies, the dipole size is very large."


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  • (Score: 2) by Barenflimski on Wednesday September 11 2019, @08:30PM (1 child)

    by Barenflimski (6836) on Wednesday September 11 2019, @08:30PM (#892888)

    This is how I think of all of this. To me it seems to make sense in terms of a wave.

    If a Gluon is accelerated, the potential energy rises, so therefore the gluon-wave/particle will resonate at a higher frequency, thereby allowing it to split into smaller "gluons." I simply have trouble imagining that there is a sticky particle. I can imagine a wave of energy that is say negatively charged that holds together two positively charged gluons. Again, this is simply my laymans terms for this as I have no idea about the actual charges, this is more of a metaphor for me at this point. Does that make sense?

    Maybe someone can help me out and tell me which version of Physics this falls into. I enjoy the Copenhagen view of Physics. I find Pilot wave theory interesting. I don't believe that there are separate particles and waves though. It seems to me that they are one in the same and that particles are the physical manifestation of waves. It seems to me that the particles condensate (for lack of a better word) out of the wave.

    Can someone help me out... is that view the same as the Copenhagen view? Is there another view out there that I've missed being an armchair physicist?

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  • (Score: 3, Interesting) by hendrikboom on Wednesday September 11 2019, @09:12PM

    by hendrikboom (1125) Subscriber Badge on Wednesday September 11 2019, @09:12PM (#892903) Homepage Journal

    I like the so-called multiple universes interpretation, because that's a direct interpretation of the mathematics. Though I like to call it relative state theory, because I like to emphasize that the state of any system is relative to the observer.

    And if you assume that there's essentially one observer (who is the totality of classical physical reality) it specializes down to the Copenhagen interpetation.

    As for particles versus waves, I have to go to my own armchair physics. When you observe something, you hit it with a measurement operator, and the something jumps into a state that is one of the eigenstates of the operator that you are measuring with. And (here comes the armchair) presumably if your operator is one whose eigenstates are particles, you get particles.

    -- hendrik