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Category: particle physics – Page 19

Scientists observe collective behavior of femtoscopic droplets at CERN

At CERN’s Large Hadron Collider (LHC), lead atom nuclei, accelerated in opposite directions, collide at speeds close to the speed of light. In such scattering processes, the quarks and gluons that make up these nuclei collide, creating other quarks and gluons, produced by the fundamental interaction known as the “strong interaction.” The number of particles created is around one hundred times greater than the initial number.

As the particles created are numerous and interact strongly with one another, emergent phenomena arise: the whole is more than the sum of its parts. More precisely, the 30,000 or so created particles form a fluid (with droplets of femtoscopic size, 10-14 m), where their individuality disappears.

This description has the advantage of simplicity, as the fluid is characterized by a handful of parameters: (about 2,500 billion degrees) and velocity.

Nuclear Glow Illuminates Dark Matter

High-energy particles or gamma rays are usually needed to kick an atomic nucleus up to a higher-energy state. But last year, scientists excited thorium-229 nuclei with just laser light (see Viewpoint: Shedding Light on the Thorium-229 Nuclear Clock Isomer). Laser-excited nuclei could be useful for making precise timekeepers and sensitive quantum sensors. And now, Wolfram Ratzinger at the Weizmann Institute of Science in Israel and his colleagues have shown how these nuclei also provide a way to detect certain speculative particles that may constitute dark matter [1].

Several models of dark matter involve axions or other extremely light bosons. Thanks to their lightness, these particles would have to be abundant—so much so that they would collectively behave like a classical field, oscillating at a frequency proportional to their mass. The particles’ interactions with the building blocks of nuclei—quarks and gluons—would cause various nuclear properties to oscillate at that same frequency. Among those properties is the energy of the photon emitted by an excited thorium-229 nucleus. Crucially, the oscillations in that energy are predicted to be much more pronounced, and therefore easier to detect, than those in other properties.

Ratzinger and his colleagues conducted the first-ever search for these oscillations in a previously reported spectrum of light emitted by excited thorium-229 nuclei. Finding no oscillations, the researchers set upper limits on the coupling strength of ultralight dark matter particles to quarks and gluons for particles ranging in mass from 10–20 to 10–13 eV. These limits are less stringent than those obtained through other means, but the team anticipates that ongoing and future experiments could set much stronger and possibly decisive constraints.

Astrophysicists explore our galaxy’s magnetic turbulence in unprecedented detail using a new computer model

Astronomers have developed a computer simulation to explore, in unprecedented detail, magnetism and turbulence in the interstellar medium (ISM)—the vast ocean of gas and charged particles that lies between stars in the Milky Way galaxy.

Described in a study published in Nature Astronomy, the model is the most powerful to date, requiring the computing capability of the SuperMUC-NG supercomputer at the Leibniz Supercomputing Center in Germany. It directly challenges our understanding of how magnetized turbulence operates in astrophysical environments.

James Beattie, the paper’s lead author and a postdoctoral researcher at the Canadian Institute for Theoretical Astrophysics (CITA) at the University of Toronto, is hopeful the model will provide new insights into the ISM, the magnetism of the Milky Way galaxy as a whole, and astrophysical phenomena such as star formation and the propagation of cosmic rays.

Researchers establish fundamental limit on how light bosonic dark matter can be

In a new study published in Physical Review Letters, scientists have estimated a new lower bound on the mass of ultra-lightweight bosonic dark matter particles.

Purported to make up about 85% of the matter content in the universe, dark matter has eluded direct observation. Its existence is only inferred by its gravitational effects on cosmic structures.

Because of this, scientists have been unable to identify the nature of dark matter and, therefore, its mass. According to our current model of quantum mechanics, all fundamental particles must be either fermions or bosons.

Theoretical framework refines understanding of the strong nuclear force

A new study published in Physical Review D titled, “Extending the Bridge Connecting Chiral Lagrangians and QCD Gaussian Sum-Rules for Low-Energy Hadronic Physics,” offers significant advancements in the understanding of the strong nuclear force. This fundamental interaction is responsible for holding protons and neutrons together within atomic nuclei and plays a central role in the formation of matter.

Dr. Amir Fariborz, Professor of Physics at SUNY Polytechnic Institute, has co-authored the research, which builds on a theoretical bridge first proposed by Dr. Fariborz and his collaborators in 2016, which connects the complex world of hadrons (composite particles such as protons, neutrons, and mesons) with their underlying quark structure.

The current work enhances this framework by incorporating higher-order effects, which allow for more refined predictions and the potential to study more intricate subatomic phenomena. These include scalar and pseudoscalar mesons that possess hybrid -gluon structures and may exhibit mixing with glueballs, a type of particle hypothesized to be composed entirely of gluons.

Applicability of a key quantum law extended to simulation conditions for systems with long-range interactions

The findings are published in the journal Physical Review Letters.

Compared with their classical counterparts, systems made up of many quantum particles—such as quantum computers—are horrendously complex to analyze and simulate. This complexity is due in part to the strong correlations between particles, which can act over long distances.

Bismuth’s mask uncovered: Implications for quantum computing and spintronics materials

Whether bismuth is part of a class of materials highly suitable for quantum computing and spintronics was a long‑standing issue. Kobe University research has now revealed that the true nature of bismuth was masked by its surface, and in doing so uncovered a new phenomenon relevant to all such materials.

The team have published their results in a letter in the journal Physical Review B.

There is a class of materials that are insulators in their bulk, but robustly conductive at their surface. As this conductivity does not suffer from defects or impurities, such “topological materials,” as they are called, are expected to be highly suitable for use in quantum computers, spintronics and other advanced electronic applications.