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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."


Original Submission

 
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  • (Score: 2) by hendrikboom on Thursday September 12 2019, @01:19AM (2 children)

    by hendrikboom (1125) Subscriber Badge on Thursday September 12 2019, @01:19AM (#893008) Homepage Journal

    The summary left out one of he more interesting lines in the original paper.

    We observed, for the first time, that the CMS data show a clear deviation from the linear QCD model at their highest energy point.

    If this is what it seems to be (perhaps a big IF) this is intriguing. There has been speculation for a while that the quantum mechanics we know is but a linear low-energy approximation to another, more comprehensive, nonlinear high-energy physics. If that's true, we need the nonlinearity to truly understand black holes, big bangs, and the like.

    I've seem the blackboard-sized equations for the Lagrangian of all physics taken together, and wondered, isn't there something simpler that this can be derived from? Maybe by differentiation or maximization or some such?

    I've been given hope when someone took the Lagrangian for general relativity (the one that gives rise to Einstein's field equation) and introduced one more source of variability -- that the gravitational constant G, the speed of light, and one other number (I forget what) might not be in constancy with respect to one another, but they can vary. This gave one other thing to vary into the minimization math, and out came the Einsteinian field equations with a cosmological constant, with a specific value, and that value matched observed astronomical results.

    So this is a case where something was gained from a more general framework. Could the same happen with a nonlinear quantum mechanics?

    - hendrik

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  • (Score: 1, Funny) by Anonymous Coward on Thursday September 12 2019, @03:57AM (1 child)

    by Anonymous Coward on Thursday September 12 2019, @03:57AM (#893048)

    If you differentiate 42 then... it gets complicated. Don't do that.