Physics News and Discussions

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caltrek
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Matter and Antimatter Seem to Respond Equally to Gravity
January 5, 2022

https://www.eurekalert.org/news-releases/939319

Introduction:
(EurekAlert) As part of an experiment to measure—to an extremely precise degree—the charge-to-mass ratios of protons and antiprotons, the RIKEN-led BASE collaboration at CERN, Geneva, Switzerland, has found that, within the uncertainty of the experiment, matter and antimatter respond to gravity in the same way.

Matter and antimatter create some of the most interesting problems in physics today. They are essentially equivalent, except that where a particle has a positive charge its antiparticle has a negative one. In other respects they seem equivalent. However, one of the great mysteries of physics today, known as “baryon asymmetry,” is that, despite the fact that they seem equivalent, the universe seems made up entirely of matter, with very little antimatter. Naturally, scientists around the world are trying hard to find something different between the two, which could explain why we exist.

As part of this quest, scientists have explored whether matter and antimatter interact similarly with gravity, or whether antimatter would experience gravity in a different way than matter, which would violate Einstein’s weak equivalence principle. Now, the BASE collaboration has shown, within strict boundaries, that antimatter does in fact respond to gravity in the same way as matter.

The finding, published in Nature, actually came from a different experiment, which was examining the charge-to-mass ratios of protons and antiprotons, one of the other important measurements that could determine the key difference between the two.
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weatheriscool
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Physicists detect a hybrid particle held together by uniquely intense 'glue'
https://phys.org/news/2022-01-physicist ... quely.html
by Jennifer Chu, Massachusetts Institute of Technology

In the particle world, sometimes two is better than one. Take, for instance, electron pairs. When two electrons are bound together, they can glide through a material without friction, giving the material special superconducting properties. Such paired electrons, or Cooper pairs, are a kind of hybrid particle—a composite of two particles that behaves as one, with properties that are greater than the sum of its parts.

Now MIT physicists have detected another kind of hybrid particle in an unusual, two-dimensional magnetic material. They determined that the hybrid particle is a mashup of an electron and a phonon (a quasiparticle that is produced from a material's vibrating atoms). When they measured the force between the electron and phonon, they found that the glue—or bond—was 10 times stronger than any other electron-phonon hybrid known to date.

The particle's exceptional bond suggests that its electron and phonon might be tuned in tandem; for instance, any change to the electron should affect the phonon, and vice versa. In principle, an electronic excitation, such as voltage or light, applied to the hybrid particle could stimulate the electron as it normally would, and also affect the phonon, which influences a material's structural or magnetic properties. Such dual control could enable scientists to apply voltage or light to a material to tune not just its electrical properties but also its magnetism.

The results are especially relevant, as the team identified the hybrid particle in nickel phosphorus trisulfide (NiPS3), a two-dimensional material that has attracted recent interest for its magnetic properties. If these properties could be manipulated, for instance through the newly detected hybrid particles, scientists believe the material could one day be useful as a new kind of magnetic semiconductor, which could be made into smaller, faster, and more energy-efficient electronics.
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andmar74
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https://www.newscientist.com/article/mg ... f-physics/
[At half past six on the evening of 20 January 2021, amid the gloom of a long winter lockdown, a small team met on Zoom to share a moment they knew might change physics forever. “I was literally shaking,” says Mitesh Patel at Imperial College London. He and his team were about to “unblind” a long-awaited measurement from the LHCb experiment at the CERN particle physics laboratory near Geneva, Switzerland – one that might, at long last, break the standard model, our current best picture of nature’s fundamental workings.

The measurement concerns subatomic particles known as “beauty” or “bottom” quarks. Over the past few years, their behaviour has hinted at forces beyond our established understanding. Now, with the hints continuing to firm up, and more results imminent, it’s crunch time. If these quarks are acting as they appear to be, then we are not only seeing the influence of an unknown force of nature, but perhaps also the outline of a new, unified theory of particles and forces.

That is a big if – but many particle physicists are on tenterhooks, myself included.”I’ve never seen something like this,” says Gino Isidori, a theorist at the University of Zurich, Switzerland. “I’ve never been so excited in my life.”

For all its dazzling success in describing the basic ingredients of our universe, the standard model of particle physics has many shortcomings. It can’t explain dark matter, the invisible stuff that keeps galaxies from flying apart, or dark energy, which seems to be driving the accelerating expansion of the universe. Nor can it tell us how matter survived the big bang, rather …



Read more: https://www.newscientist.com/article/mg ... YqgE/quote]
weatheriscool
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New insight into the internal structure of the proton
https://phys.org/news/2022-01-insight-i ... roton.html
by ATLAS Experiment
While the Large Hadron Collider (LHC) at CERN is well known for smashing protons together, it is actually the quarks and gluons inside the protons—collectively known as partons—that are really interacting. Thus, in order to predict the rate of a process occurring in the LHC—such as the production of a Higgs boson or a yet-unknown particle—physicists have to understand how partons behave within the proton. This behavior is described in parton distribution functions (PDFs), which describe what fraction of a proton's momentum is taken by its constituent quarks and gluons.

Knowledge of these PDFs has traditionally come from lepton–proton colliders, such as HERA at DESY. These machines use point-like particles, such as electrons, to directly probe the partons within the proton. Their research revealed that, in addition to the well-known up and down valence quarks that are inside a proton, there is also a sea of quark–antiquark pairs in the proton. This sea is theoretically made of all types of quarks, bound together by gluons. Now, studies of the LHC's proton–proton collisions are providing a detailed look into PDFs, in particular the proton's gluon and quark-type composition.
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A well-known iron-based magnet is also a potential quantum information material
https://phys.org/news/2022-01-well-know ... antum.html
by Ames Laboratory

Scientists pursuing better performance in a well-known type of iron-based magnet also discovered wide-gap semiconducting behavior and a quantum state useful for quantum information processing—all in a single low-cost material that has been in existence for decades.

Scientists at the U.S. Department of Energy's Critical Materials Institute, or CMI, study ways to make lower-cost, easier-to-obtain materials used as ingredients in technologies that are in demand now or are developing for the future. In this case, the researchers were investigating ways to create a stronger iron-based permanent magnet, something referred to as a "gap" magnet.

Permanent magnets fall into two broad categories. The strongest-performing permanent magnets contain rare-earth metals like samarium, neodymium, and dysprosium—their properties make them the best and often only choice for applications like computer hard disk drives and motors in hybrid and electric vehicles. These magnets are typically expensive, and their rare-earth components can be difficult to obtain. The second, iron-based permanent magnets, are inexpensive and made of readily available materials, but their performance is often too poor for many advanced applications. In between the high performing rare-earth magnets and low-performing iron-based magnets is a "gap," where there is a great need for permanent magnets that perform in the mid-range of desirable properties. Filling that gap reduces the need for rare-earth magnets, and in turn hard to source rare-earth materials.
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Advances in theoretical modeling of atomic nuclei
https://phys.org/news/2022-01-advances- ... uclei.html
by Ana Lopes, CERN
The atomic nucleus is a tough nut to crack. The strong interaction between the protons and neutrons that make it up depends on many quantities, and these particles, collectively known as nucleons, are subject to not only two-body forces but also three-body ones. These and other features make the theoretical modeling of atomic nuclei a challenging endeavor.

In the past few decades, however, ab initio theoretical calculations, which attempt to describe nuclei from first principles, have started to change our understanding of nuclei. These calculations require fewer assumptions than traditional nuclear models, and they have a stronger predictive power. That said, because so far they can only be used to predict the properties of nuclei up to a certain atomic mass, they cannot always be compared with so-called DFT calculations, which are also fundamental and powerful and have been around for longer. Such a comparison is essential to build a nuclear model that is applicable across the board.

In a paper just published in Physical Review Letters, an international team at CERN's ISOLDE facility shows how a unique combination of high-quality experimental data and several ab initio and DFT nuclear-physics calculations has resulted in an excellent agreement between the different calculations, as well as between the data and the calculations.
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Arase satellite uncovers coupling between plasma waves and charged particles in Geospace
https://phys.org/news/2022-01-arase-sat ... lasma.html
by Nagoya University
In a new study published in Physical Review Letters, researchers from Japan show that high-frequency plasma waves in the geospace can generate low-frequency plasma waves through wave-particle interactions by heating up low-energy ions, unveiling a new energy transfer pathway in collisionless plasma.

A prominent signature of plasma—a state of matter characterized by freely roaming charged particles interacting via electromagnetic forces—is the generation of "plasma waves," resulting from an instability of plasma distributions. "Fast magnetosonic waves" (MSWs) are one kind of electromagnetic plasma wave in the geospace. MSWs result from hot protons and are considered "high frequency waves."

Another kind of wave commonly generated in the geospace is the "electromagnetic ion cyclotron" (EMIC) wave, which is considered a "low frequency wave." Recently, satellite observations in the geospace have shown that MSWs and EMIC waves often occur together. However, the mechanism underlying this co-occurrence has remained unclear.
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Fastest-ever study of how electrons respond to X-rays performed
https://phys.org/news/2022-01-fastest-e ... -rays.html
by Hayley Dunning, Imperial College London
A study of electron dynamics timed to millionths of a billionth of a second reveals the damage radiation can do on a molecular level.

The first-of-its kind study used ultrafast X-ray laser pulses to disrupt the electrons in a molecule of nitrous oxide and measure the resultant changes with unprecedented accuracy.

The work, published today in Science, was performed at the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Centre (SLAC), Stanford, U.S. and was supported by a team of five scientists from Imperial College London.

Conventional X-rays used in imaging and radiotherapy can cause damage to cells, but exactly how on a molecular level is not known. Additionally, new high-intensity and short-pulse-duration X-ray lasers are being proposed to image smaller molecules with greater precision, leading to questions about potential damage this could cause to living tissue.

For the first time, researchers have been able to measure the behavior of electrons in a molecule as it responded to irradiation by ultrafast X-rays on attosecond timescales—less than millionths of a billionth of a second.

Understanding to new limits

Co-author Professor Jon Marangos, from the Department of Physics at Imperial, said: "Being able to reach a few hundred attosecond precision when timing electron dynamics means we can now begin to understand certain phenomena to new limits.
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Physicist solves century old problem of radiation reaction
https://phys.org/news/2022-01-physicist ... ction.html
by Lancaster University
A Lancaster physicist has proposed a radical solution to the question of how a charged particle, such as an electron, responded to its own electromagnetic field.

This question has challenged physicists for over 100 years but mathematical physicist Dr. Jonathan Gratus has suggested an alternative approach—published in the Journal of Physics A: Mathematical and Theoretical with controversial implications.

It is well established that if a point charge accelerates it produces electromagnetic radiation. This radiation has both energy and momentum, which must come from somewhere. It is usually assumed that they come from the energy and momentum of the charged particle, damping the motion.

The history of attempts to calculate this radiation reaction (also known as radiation damping) date back to Lorentz in 1892. Major contributions were then made by many well known physicists including Plank, Abraham, von Laue, Born, Schott, Pauli, Dirac and Landau. Active research continues to this day with many articles published every year.

The challenge is that according to Maxwell's equations, the electric field at the actual point where the point particle is, is infinite. Hence the force on that point particle should also be infinite.

Various methods have been used to renormalise away this infinity. This leads to the well established Lorentz-Abraham-Dirac equation.
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Observation of quantum transport at room temperature in a 2.8-nanometer CNT transistor
https://techxplore.com/news/2022-02-qua ... r-cnt.html
by National Institute for Materials Science
An international joint research team led by the National Institute for Materials Science (NIMS) has developed an in situ transmission electron microscopy (TEM) technique that can be used to precisely manipulate individual molecular structures. Using this technique, the team succeeded in fabricating carbon nanotube (CNT) intramolecular transistors by locally altering the CNT's helical structure, thereby making a portion of it to undergo a metal-to-semiconductor transition in a controlled manner.

Semiconducting CNTs are promising as the channel material for energy-efficient nanotransistors which may be used to create microprocessors superior in performance to currently available silicon microprocessors. However, controlling the electronic properties of CNTs by precisely manipulating their helical structures has been a major challenge.

This joint research team succeeded for the first time in controllably manipulating CNTs' electronic properties by locally altering their helical structures using heat and mechanical strain. Using this technique, the team was then able to fabricate CNT transistors by converting a portion of a metallic CNT into a semiconductor, where the semiconductor nanochannel was covalently bonded to the metallic CNT source and drain. The CNT transistors, with the channel as short as 2.8 nanometers in length, exhibited coherent quantum transport at room temperature—wave-like electron behavior usually observed only at extremely low temperature.

The molecular structure manipulation technique developed in this research may potentially be used to fabricate innovative nanoscale electronic devices. The team plans to use this technique to engineer material structures with atomic-level precision to fabricate electronic and quantum devices composed of individual atomic structures or molecules.
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