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Category: particle physics

Piezoelectric materials enable a new approach to searching for axions

Dark matter, a type of matter that does not emit, reflect or absorb light, is predicted to account for most of the matter in the universe. As it eludes common experimental techniques for studying ordinary matter, understanding the nature and composition of dark matter has so far proved very challenging. One hypothesis is that it is made up of hypothetical particles known as quantum chromodynamics (QCD) axions. These are theoretical elementary particles that would interact very weakly with ordinary matter and are predicted to be extremely light, highly stable and electrically neutral.

While several large-scale studies have searched for small signals or effects that would indicate the presence of these particles or their interaction with ordinary matter, their existence has not yet been confirmed experimentally. In a paper recently published in Physical Review Letters, researchers at Perimeter Institute, University of North Carolina, Kavli Institute and New York University have introduced a new approach to search for QCD axions using a class of materials that generate electric fields when deformed, called piezoelectric materials.

“The axion was proposed in the late 1970s by Weinberg and Wilczek, as a solution to the strong CP (Charge-Parity) problem, a long-standing puzzle in the theory of the strong nuclear force,” Amalia Madden, co-senior author of the paper, told Phys.org.

Physicists create optical phenomenon inspired by the quantum Hall and spin Hall effects

Researchers at the Würzburg site of the Cluster of Excellence ctd.qmat have succeeded in transferring the topological quantum Hall and spin Hall effects to a hybrid light-matter system by harnessing targeted material design. The team led by Professor Sebastian Klembt generated this optical quantum phenomenon by using polaritons—hybrid light-matter particles. This advance paves the way for optical information processing. The results have been published in Nature Communications.

Back in 1980, Nobel laureate Klaus von Klitzing, then working in Würzburg, first demonstrated topological charge transport with the quantum Hall effect.

In 2006, Professor Laurens Molenkamp at JMU Würzburg provided the world’s first experimental evidence of the quantum spin Hall effect as an intrinsic property of a topological insulator. Both phenomena protect electrons from scattering.

Scientists observe atoms existing in two places at once for the first time

In a world-first, quantum physicists at ANU have observed atoms entangled in motion. Their experiment using helium atoms, represents a major advancement on similar experiments using photons, which are particles of light.

But unlike photons, helium atoms have mass and experience gravity.

Read the full article in Nature Communications:
https://www.nature.com/articles/s4146… development unlocks new ways to examine one of the biggest unanswered questions about the universe: how does the small-scale physics of quantum mechanics interact with gravity and general relativity at the universal scale? By observing quantum entanglement in atoms for the first time, are we one small step closer to finding out whether the “Theory of Everything” is not just hot air?

This development unlocks new ways to examine one of the biggest unanswered questions about the universe: how does the small-scale physics of quantum mechanics interact with gravity and general relativity at the universal scale?

By observing quantum entanglement in atoms for the first time, are we one small step closer to finding out whether the “Theory of Everything” is not just hot air?

For more visit https://science.anu.edu.au/

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Neutrinos Make a Break in the Ice

The spectrum of cosmic neutrinos can unmask the types of astrophysical sources that produce these and other high-energy particles. The IceCube Neutrino Observatory, whose detectors lie buried in Antarctic ice, has been measuring cosmic neutrinos since 2010. Early data releases suggested that the neutrino spectrum is a single falling power law, which is consistent with simple models relating cosmic neutrinos to cosmic rays. But now, after 14 years of observation, IceCube’s data show evidence for a break, or knee-like downward bend, in the spectrum at an energy of around 30 tera-electron-volts [1, 2]. Such a break could evince a mix of neutrino sources.

Cosmic neutrinos are predominantly generated whenever high-energy cosmic rays collide with other particles. The neutrino spectrum can therefore reveal information about how and where cosmic rays are accelerated. If the acceleration takes place exclusively in shock environments, where collisions produce neutrinos, the neutrino spectrum would be a single power law. However, the latest analysis of neutrino data by the IceCube Collaboration has uncovered a more complex spectrum. The researchers sifted through a decade’s worth of neutrino observations using improved models of both backgrounds and detector uncertainties. The results show a spectrum break with a statistical confidence of 4 sigma (where 5 sigma constitutes a bona fide detection).

The break could mean that neutrinos come from more than one source class, with each class having a different way of accelerating cosmic rays, says collaboration member Vedant Basu from the University of Utah. He also points out that the observed shape of the neutrino spectrum is consistent with predictions based on the properties of the diffuse gamma-ray background, supporting models that assume the two types of particles originate from the same sources.

Quantum experiment shows events may have no fixed order

For the first time, a team of physicists in Austria has carried out an experiment that appears to verify the principle of indefinite causal order: an idea that suggests that timelines of events can exist in multiple orders at the same time. Led by Carla Richter at the Vienna Center for Quantum Science and Technology, the researchers hope their result could finally allow physicists to verify a key prediction of quantum theory. The results have been published in PRX Quantum.

The basic principle of cause and effect underpins everything that happens in the classical world: for an event to occur, it must be triggered by another event in its past. Yet in the quantum world, physicists have long suspected that these rules may not always apply.

Just as quantum particles can exist in superpositions of multiple states which collapse to a single outcome when measured, indefinite causal order suggests something similar may apply to entire sequences of events. Until a measurement is made, multiple orders of cause and effect can exist in superposition.

Experimental evidence shows how photons spread across multiple paths in an interferometer

The nature of quantum particles has long puzzled scientists. While single-particle interference suggests that a photon can behave like a spread-out wave, a whole photon is only ever detected in one specific place. Traditional interpretations of quantum mechanics often address this by suggesting the particle is in a superposition of being here and there at the same time. However, this tells us only where the particle is when it is measured, not where the particle physically is when no detector is present.

A research team led by Hiroshima University, led by Holger F. Hofmann, professor at the Graduate School of Advanced Science and Engineering, has now developed a method to measure this delocalization without disturbing the photon’s wave-like path.

In a study published in the New Journal of Physics, the researchers applied a modification of the well-established method of “weak measurements” to a two-path interferometer. As the photon traveled, they applied a tiny rotation by a positive angle in one path and a negative angle in the other. If the two paths interfere in the output, the average rotation angle is always zero. However, this is only a statistical average.

‘Near-misses’ in particle accelerators can illuminate new physics, study finds

Particle accelerators reveal the heart of nuclear matter by smashing together atoms at close to the speed of light. The high-energy collisions produce a shower of subatomic fragments that scientists can then study to reconstruct the core building blocks of matter.

An MIT-led team has now used the world’s most powerful particle accelerator to discover new properties of matter, through particles’ “near-misses.” The approach has turned the particle accelerator into a new kind of microscope—and led to the discovery of new behavior in the forces that hold matter together.

In a study appearing this week in the journal Physical Review Letters, the team reports results from the Large Hadron Collider (LHC)—a massive underground, ring-shaped accelerator in Geneva, Switzerland. Rather than focus on the accelerator’s particle collisions, the MIT team searched for instances when particles barely glanced by each other.

Hearing research traces evolution of key inner ear protein

In the intricate machinery of the inner ear, hearing begins with a protein that moves a few billionths of a meter up to 100,000 times per second. That protein, called TMC1, sits at the tips of sensory hair cells deep in the snail-shaped cochlea. When sound waves move these microscopic hairs, TMC1 acts as a channel, opening and allowing charged particles to flow into the cell and trigger an electrical signal to the brain.

Without TMC1, that signal never starts. Mutations in the TMC1 gene are a well-known cause of hereditary hearing loss in humans. Because of this central role, TMC1 is an attractive target for researchers designing gene therapies aimed at restoring hearing. Several groups are testing ways to supply working copies of the gene or fix harmful mutations.

For these efforts to be safe and effective, scientists need to know in detail how TMC1 is built, how it opens, and which parts of the protein are most sensitive to change. However, the hair-cell system that includes TMC1 is so complex, sensitive, and hard to access that it is notoriously difficult to take apart and study directly.

‘Cool’ detectors cut neutrino mass upper limit by an order of magnitude

Their mass is extremely low, but how light are neutrinos really? A collaboration comprising German and international research groups has optimized its experiments to determine the mass of these “ghost particles.” In doing so, they succeeded in further adjusting downward the upper limit on the neutrino mass scale that had previously been determined in similar experiments. The study is published in the journal Physical Review Letters.

As part of the “Electron Capture in Ho-163 Experiment” (ECHo), the researchers are using the isotope Holmium-163 (Ho-163), whose decay processes allow for conclusions on the neutrino mass. According to ECHo spokesperson Prof. Dr. Loredana Gastaldo, a scientist at Heidelberg University’s Kirchhoff Institute for Physics, the current results verify that even larger-scale investigations will be feasible in future to get even closer to the mass of neutrinos and ultimately precisely determine it.

Neutrinos are elementary particles with extremely low mass that have no electrical charge. Because their interaction with matter is very weak, the properties of these “ghost particles” are very difficult to determine. This is especially true for the neutrino mass, which has yet to be precisely measured, with only its upper limit being known. According to Gastaldo, determining the mass could pave the way for new theoretical models beyond the standard model of particle physics and thereby contribute to a better understanding of the evolution of our universe.

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