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Category: particle physics – Page 2

A Widening Anomaly Strains the Standard Model

Does a new measurement of a rare decay of the neutral B meson portend new physics?

In particle physics, ten years is a long time to sit with a puzzle. Since 2013, measurements of a rare decay—a neutral B meson (B0) transforming into an excited kaon (K*0) and a muon–antimuon pair (µ+µ –)—have stubbornly refused to match the predictions of the standard model, the theory that describes all known particles and forces [1]. Small enough to be dismissed at first as a statistical fluctuation, the pattern of discrepancies has grown with each new dataset into one of the most tantalizing hints of new physics in experimental particle physics. Now the LHCb Collaboration at CERN in Switzerland has published its most comprehensive analysis of the decay to date [2]. The result is clear: The anomaly persists. Encouragingly, the theoretical and experimental tools to understand it have never been sharper.

Within the mathematical framework of the standard model, the decay in question, B0 → K*0µ+µ–, can occur only through so-called higher-order electroweak loop diagrams in which a bottom, or b, quark transforms into a strange, or s, quark [3]. As a result, the decay is extraordinarily rare. In every million B-meson decays of all kinds, you can expect to find only one. That rarity makes the decay valuable: It could bear measurable imprints of particles beyond the standard model that contribute to the same loop processes but have so far escaped detection because they are too heavy.

Catching hydrogen in the act: Tracking the absorption process over time

If you’re looking for hydrogen on the elemental chart, it won’t take you long to find it. It is right there at the beginning, the lightest possible material. One electron, one proton, one neutron. Simple, minimalistic, the Marie Kondo of the elemental chart, but with enormous potential in terms of possible technological applications.

A very prominent example interests every single one of us: Let’s look into the daytime sky.

If we think of the sun as a furnace, then hydrogen atoms are the coal ingots.

Why some glasses break suddenly while others deform smoothly

If a liquid is cooled slowly to its freezing point, it becomes a crystal in which the constituent particles are arranged in an ordered pattern. In contrast, when the liquid is cooled very quickly, the particles are unable to arrange themselves in an ordered fashion, and it becomes glass. Glassy materials are all around us in everyday life. Common examples include window glass, certain metal alloys, polymers, foams, gels and even soft materials like emulsions and colloids.

These materials can behave very differently when an external force is applied to them, such as bending, stretching or compressing. Some materials change shape slowly and smoothly under strain (this property is called ductility). Some materials may resist deformation at first but then suddenly break or crack without warning (this property is called brittleness). Whether a material bends or breaks determines how safely and reliably it can be used in everyday objects and engineering applications.

Scientists broadly classify glasses into two types: strong and fragile glasses.

Hackers exploit Roundcube flaw to spy on academic researchers

A China-linked threat cluster has been exploiting vulnerable Roundcube servers at U.S. and Canadian universities to steal credentials and deploy backdoor malware.

The campaign has been observed since May and focuses on physics and engineering departments, administrators and professors, as well as organizations involved in astrophysics, particle physics, or national security-related research.

Researchers at cybersecurity company Proofpoint are tracking the activity under the name ‘UNK_MassTraction’ and believe to be associated with a new threat cluster.

Evidence of elusive high-energy gravitons in quantum Hall systems

Electrons, negatively charged particles, sometimes coordinate their movements in ways that produce certain collective excitations referred to as quasiparticles. One case in which this occurs is the quantum Hall effect, a phenomenon that emerges when electrons are confined to a very thin layer, cooled to temperatures around 0 kelvin and exposed to a very strong magnetic field.

A framework called parton theory hypothesized the existence of emergent partons (i.e., quark-like quasiparticles in condensed matter physics that should not be confused with quarks and gluons in particle physics) to explain the collective excitations of quantum Hall states.

Recent geometric theoretical frameworks also suggest that small fluctuations in a system’s quantum metric (i.e., a quantity describing the ‘shape’ of a quantum state) produce collective spin-2 excitations referred to as chiral gravitons.

Quantum computers model nine fusion fuel material configurations for first time

A team of scientists from Oak Ridge National Laboratory, Cleveland Clinic and IBM has calculated nine molecular configurations of a promising material to produce fuel for fusion energy—the first known instance of such computations on quantum computers.

Such calculations, demonstrated in a new paper published on the arXiv preprint server, are computationally challenging for classical computers to scale when working alone. They are a fundamental step toward optimizing the production and extraction of tritium—an extremely rare material in nature that is necessary to produce fusion energy with most of the proposed machines. Ensuring adequate supplies of tritium has long been a barrier to realizing the promise of clean, abundant energy from fusion power plants, and solving this issue is a key objective of the U.S. Department of Energy’s Genesis Mission.

Quantum computers are well-suited to computing the atomic-level chemistry of a liquid salt that contains fluorine, lithium and beryllium (FLiBe), one of the leading candidate materials for extracting tritium fuel in fusion reactors. To compute different configurations of clusters of FLiBe, the team used the same quantum-centric supercomputing techniques now being applied to 12,635-atom protein simulations with Cleveland Clinic. These methods can calculate the quantum behavior of electrons in complex materials, complementing and enhancing the capabilities of classical supercomputers and algorithms.

Magnetic octupole model captures domain-wall motion in noncollinear antiferromagnets

Researchers from The Grainger College of Engineering at the University of Illinois Urbana-Champaign have developed the first magnetic multipole-based micromagnetic model for antiferromagnets. Published in Applied Physics Reviews, their generalized framework provides a theoretical and computational foundation for designing future spintronic devices made with antiferromagnetic materials.

Unlike traditional electronics, which rely on an electron’s charge, spin electronics harnesses an electron’s magnetic orientation (spin). In recent years, materials science researchers have identified antiferromagnets as a promising material for future spintronic devices because of their ultrafast spin dynamics and stability under external magnetic fields.

But before these materials can be implemented in practical devices, researchers need robust models that decipher their complex, nonuniform movements. Although micromagnetic simulations have been widely used to study spin dynamics in ferromagnets, a comparable framework had yet to be fully established for antiferromagnets, whose spin structure is more difficult to control. However, some types of antiferromagnets—such as noncollinear antiferromagnets—have a unique rotating structure that is more easily manipulated.

Pressure unlocks 3D superconductivity in tantalum disulfide at triple the temperature

Superconductors have long been considered a promising technology for the energy systems of the future. They can conduct electricity without resistance, thus eliminating both conduction losses and waste heat. Up to now, however, superconductors have only been applied in special cases, as in the immensely powerful magnet coils of particle accelerators such as the Large Hadron Collider at CERN. This is because superconductors must be well cooled, down to extremely low temperatures for some materials.

In the future, novel materials with special quantum properties are expected to make superconductivity possible at less frosty and more easily achievable subzero temperatures. A research team led by Zurab Guguchia at the Paul Scherrer Institute PSI has now provided the first comprehensive characterization of such a quantum material. This should contribute to a detailed understanding of these processes and facilitate the search for technologically usable superconductors. The results are published in the journal Nature Communications.

“Currently, research is being conducted worldwide on novel, unconventional superconductors that exhibit robust superconductivity even at higher temperatures or in strong external magnetic fields,” Guguchia says. The physicist is a research group leader in the PSI Center for Neutron and Muon Sciences and works with his team on the materials of the future.

Atomic ‘domino effect’ found to drive phase changes in a two-dimensional crystal

Phase transformations—in which a material changes from one crystal structure to another, thereby acquiring dramatically different properties—are ubiquitous in nature. Understanding the microscopic mechanisms of these transformations is essential for controlling material properties and designing functional devices.

A research team led by Profs. Chen Xingqiu and Sun Yan from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences, in collaboration with Prof. Niu Haiyang from Northwestern Polytechnical University, has uncovered a previously unknown phase transformation mechanism in monolayer molybdenum telluride (MoTe2).

The study, published in Proceedings of the National Academy of Sciences on June 29, reveals a phase transformation pathway that is fundamentally distinct from the conventional martensitic model, in which many atoms move together through concerted shear displacements.

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