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Category: particle physics – Page 39

MIT physicists have created a new and long-lasting magnetic state in a material, using only light.

In a study that appears in Nature, the researchers report using a —a light source that oscillates more than a trillion times per second—to directly stimulate atoms in an antiferromagnetic material. The laser’s oscillations are tuned to the natural vibrations among the material’s atoms, in a way that shifts the balance of atomic spins toward a new magnetic state.

The results provide a new way to control and switch , which are of interest for their potential to advance information processing and memory chip technology.

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Atomic simulations deepen the mystery of how engineered materials known as refractory high-entropy alloys can suffer so little damage by radiation.

Refractory high-entropy alloys are materials made from multiple high-melting-point metals in roughly equal proportions. Those containing tungsten exhibit minimal changes in mechanical properties when exposed to continuous radiation and could be used to shield the crucial components of future nuclear reactors. Now Jesper Byggmästar and his colleagues at the University of Helsinki have performed atomic simulations that explore the uncertain origins of this radiation resistance [1]. The findings could help scientists design novel materials that are even more robust than these alloys in extreme environments.

The researchers studied a tungsten-based refractory high-entropy alloy using state-of-the-art simulations guided by machine learning. In particular, they modeled the main mechanism by which radiation can disrupt such an alloy’s atomic structure. In this mechanism, the incoming radiation causes one atom in the alloy to displace another atom, forming one or more structural defects. The team determined the threshold energy needed to induce such displacements and its dependence on the masses of the two involved atoms.

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In the early moments following the Big Bang, matter and antimatter should have been created in equal amounts. However, 13.8 billion years later, the Universe is overwhelmingly made of matter, with antimatter nearly absent. This strange imbalance has baffled scientists for decades, hinting that something must have occurred to tilt the balance in favor of matter.

One of the leading theories to explain this disparity is charge–parity (CP) violation, a phenomenon predicted by the Standard Model of particle physics. CP violation refers to a small but measurable difference in how matter and antimatter behave.

However, the Standard Model predicts that the number of CP violations is far too small to account for the vast predominance of matter. So far, CP violation has only been observed in certain particle decays, notably in mesons — particles made of quarks and an antiquark. To truly understand the origins of the matter-antimatter imbalance, scientists need to see CP violation in a broader range of particles, particularly baryons, composed of three quarks.

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The LOREX experiment utilizes lorandite ore to gauge historical solar neutrino flux, revealing insights about the Sun’s development and climatic effects through advanced decay rate measurements.

The Sun, Earth’s life-sustaining powerhouse, generates immense energy through nuclear fusion while emitting a steady stream of neutrinos — subatomic particles that reveal its inner workings. While modern neutrino detectors shed light on the Sun’s current behavior, key questions remain about its stability over millions of years — a timeframe encompassing human evolution and major climate changes.

Addressing these questions is the mission of the LORandite EXperiment (LOREX), which depends on accurately determining the solar neutrino cross-section for thallium. An international team of scientists has now achieved this crucial measurement using the unique Experimental Storage Ring (ESR) at GSI/FAIR in Darmstadt. Their groundbreaking results, advancing our understanding of the Sun’s long-term stability, have been published in the journal Physical Review Letters.

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Researchers recently made a groundbreaking discovery on the nanoscale: a new type of quasiparticle found in all magnetic materials, no matter their strength or temperature. These new properties shake up what researchers previously knew about magnetism, showing it’s not as static as once believed.

“Emergent topological quasiparticle kinetics in constricted nanomagnets,” was published in Physical Review Research. The researchers include Deepak Singh and Carsten Ullrich from the University of Missouri’s College of Arts and Science, along with their teams of students and postdoctoral fellows.

“We’ve all seen the bubbles that form in sparkling water or other carbonated drink products,” said Ullrich, Curators’ Distinguished Professor of Physics and Astronomy. “The quasiparticles are like those bubbles, and we found they can freely move around at remarkably fast speeds.”

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In the Big Bang, matter and antimatter should have been created in equal amounts. But fast forward 13.8 billion years to the present day, and the universe is made almost entirely of matter, so something must have happened to create this imbalance.

The Standard Model of particle physics predicts an asymmetry between and antimatter known as charge–parity (CP) violation. But the size of this asymmetry in the Standard Model is not large enough to account for the imbalance and the asymmetry has so far been observed only in certain decays of particles called mesons, which are made of a quark and an antiquark. It remains to be seen in other meson decays and in decays of other types of particles, such as three-quark particles called baryons.

In two new articles posted to the arXiv preprint server, the LHCb collaboration at the Large Hadron Collider (LHC) reports seeing evidence of CP violation in decays of baryons and in decays of beauty hadrons into charmonium particles, shedding light on these two pieces of the matter–antimatter puzzle.

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