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Category: particle physics – Page 6

Check your ingredients’: A new blueprint for using Fermi’s ‘Golden Rule

Underpinning much of modern technology, from smartphones to scanning tunneling microscopes to particle colliders, is Fermi’s Golden Rule. Named for 20th-century Italian American physicist Enrico Fermi (but actually discovered by British physicist Paul Dirac), the rule is a formula that connects what can be measured in an experiment—such as how fast atoms “jump” between energy states—to the microscopic properties of a quantum mechanical system. The formula is taught in every undergraduate quantum physics class.

Yet scientists sometimes misapply it. They either misjudge the conditions under which the formula works, or they miss the “window” for its use. A “user manual” for Fermi’s Golden Rule would be a boon to researchers, says Yale physicist Nir Navon—and now he and his lab partners have provided one.

“We put one of the most famous formulas in all of quantum mechanics to the test, and found where it works and where it fails, including ways that many physicists weren’t fully aware of,” said Navon, an associate professor of physics in Yale’s Faculty of Arts and Sciences and senior author of a new study published in the journal Nature Physics. “We’re telling everyone who uses it to take a breath first and check their ingredients.”

China Built a Working CPU With Transistors Just 3 Atoms Thick

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Researchers develop a new way to build molecular ‘ladders’ for organic electronics

Ladder-type oligothiophenes are an important class of sulfur-containing π-conjugated molecules. Because their fused, ladder-like structures can support efficient electronic interactions, they are widely studied as core motifs for organic semiconductors, organic field-effect transistors, flexible electronics and related molecular materials.

In molecular electronics, however, simply connecting rings together is not enough. The electronic properties of these molecules depend strongly on how the thiophene rings are fused and how sulfur atoms are oriented along the molecular framework. Some arrangements produce highly conjugated systems, while others introduce cross-conjugated segments that can alter the band gap and molecular packing.

Although interest in such mixed conjugated/cross-conjugated molecular systems is growing, a general method for systematically constructing regioisomeric ladder-type oligothiophenes with precise control over thiophene ring orientation has not been well established.

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.

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