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Category: particle physics

We probably think we know gravity pretty well. After all, we have more conscious experience with this fundamental force than with any of the others (electromagnetism and the weak and strong nuclear forces). But even though physicists have been studying gravity for hundreds of years, it remains a source of mystery.

In our video Why Is Gravity Different? We explore why this force is so perplexing and why it remains difficult to understand how Einstein’s general theory of relativity (which covers gravity) fits together with quantum mechanics.

Gravity is extraordinarily weak and nearly impossible to study directly at the quantum level. We cannot scrutinize it using particle accelerators like we can with the other forces, so we need other ways to get at quantum gravity.

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Centaurs are minor planets believed to have originated in the Kuiper Belt in the outer solar system. They sometimes have comet-like features such as tails and comae—clouds of dust particles and gas—even though they orbit in a region between Jupiter and Neptune where it is too cold for water to readily sublimate, or transition, directly from a solid to a gas.

Only 18 active Centaurs have been discovered since 1927, and much about them is still poorly understood. Discovering activity on Centaurs is also observationally challenging because they are faint, telescope time-intensive and because they are rare.

A team of astronomers, led by doctoral student and Presidential Fellow Colin Chandler in Northern Arizona University’s Astronomy and Planetary Science PhD program, earlier this year announced their discovery of activity emanating from Centaur 2014 OG392, a planetary object first found in 2014. They published their findings in a paper in The Astrophysical Journal Letters, “Cometary Activity Discovered on a Distant Centaur: A Nonaqueous Sublimation Mechanism.” Chandler is the lead author, working with four NAU co-authors: graduate student Jay Kueny, associate professor Chad Trujillo, professor David Trilling and Ph.D. student William Oldroyd.

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Circa 2016 o,.o.

An international group of physicists has observed Z-boson production with two associated photons with later Z decay to electrons, muons or neutrinos at the ATLAS experiment at the Large Hadron Collider (LHC) in CERN.

Observation of this extremely rare physics process, predicted theoretically in 1960s, further validates the Standard Model ℠, according to ATLAS experiment contributor Dimitrii Krasnopevtsev.

“Such a rare process as the Z-boson production with two associated is an important test of the electro-weak sector of the Standard Model. Currently, our group has not found any deviations from theoretical predictions—in other words, we have once again confirmed Standard Model,” he explained.

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A team of European researchers discovered a new high-pressure mineral in a lunar meteorite which is helping to explain what happens to materials within the extreme pressures of the Earth’s mantle.

The new mineral donwilhelmsite is the first high-pressure mineral found in meteorites with application for terrestrial sediments dragged deep into the Earth mantle by plate tectonics. Mainly composed of calcium, aluminum, silicon, and oxygen atoms, donwilhelmsite was discovered within the Oued Awlitis 001 found in 2014 in the Western Sahara.

The meteorite is compositionally similar to rocks comprising the Earth’s continents. Eroded sediments from these continents are transported by wind and rivers to the oceans, and subducted into the Earth’s mantle as part of the dense oceanic crust. Once dragged to depths of about 460–700 km, their constituent minerals transform at high pressures and high temperatures existing at those depths into denser mineral phases, including the newly discovered mineral donwilhelmsite. In the terrestrial rock cycle, donwilhelmsite is therefore an important agent for transporting continental crustal sediments through the transition zone of the Earth’s mantle (460−700 km depth).

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Physicists at CERN’s Large Hadron Collider (LHC) are on the hunt for physics phenomena beyond the standard model. Some theories predict an as-yet undiscovered particle could be found in the form of a new resonance (a narrow peak) similar to the one that heralded the discovery of the Higgs boson in 2012.

However, Nature is not always so kind and new resonances may be so massive that their production requires collision energies beyond that of the LHC. If so, all is not lost. Just as gently sloping terrain may indicate the presence of a mountain peak ahead, LHC data may contain some hints that interesting phenomena are present at higher energy scales.

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As scientists await the highly anticipated initial results of the Muon g-2 experiment at the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory, collaborating scientists from DOE’s Argonne National Laboratory continue to employ and maintain the unique system that maps the magnetic field in the experiment with unprecedented precision.

Argonne scientists upgraded the , which uses an advanced communication scheme and new magnetic field probes and electronics to map the field throughout the 45-meter circumference ring in which the experiment takes place.

The experiment, which began in 2017 and continues today, could be of great consequence to the field of particle physics. As a follow-up to a past experiment at DOE’s Brookhaven National Laboratory, it has the power to affirm or discount the previous results, which could shed light on the validity of parts of the reigning Standard Model of particle physics.

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In 1973, physicist and later Nobel laureate Philip W. Anderson proposed a bizarre state of matter: the quantum spin liquid (QSL). Unlike the everyday liquids we know, the QSL actually has to do with magnetism—and magnetism has to do with spin.

Disordered electron spin produces QSLs

What makes a magnet? It was a long-lasting mystery, but today we finally know that magnetism arises from a peculiar property of sub-atomic particles, like electrons. That property is called “spin,” and the best—yet grossly insufficient—way to think of it is like a child’s spinning-top toy.

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Borrowing a page from high-energy physics and astronomy textbooks, a team of physicists and computer scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has successfully adapted and applied a common error-reduction technique to the field of quantum computing.

In the world of subatomic particles and giant particle detectors, and distant galaxies and giant telescopes, scientists have learned to live, and to work, with uncertainty. They are often trying to tease out ultra-rare particle interactions from a massive tangle of other particle interactions and background “noise” that can complicate their hunt, or trying to filter out the effects of atmospheric distortions and interstellar dust to improve the resolution of astronomical imaging.

Also, inherent problems with detectors, such as with their ability to record all particle interactions or to exactly measure particles’ energies, can result in data getting misread by the electronics they are connected to, so scientists need to design complex filters, in the form of computer algorithms, to reduce the margin of error and return the most accurate results.

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A team of researchers from China, Spain, Russia and Portugal has developed a way to use Moiré lattices to optically induce and highlight the formation of optical solitons under different geometrical conditions. In their paper published in the journal Nature Photonics, the group describes their work, which involved using photorefractive nonlinear media as a means of localizing laser light into tight spots.

Solitons are quasiparticles propagated by a traveling wave. Unlike waves such as those produced in water, solitons are neither followed nor preceded by other such waves—they also hold their shape as they move. They are important because they are able to prevent diffraction from occurring, which is why they play such an important role in telecommunications and other information carrier systems. Moiré lattices are patterns that sometimes emerge in printed or scanned images when two patterns overlap one another in an offset fashion. They have been used in graphene-based research efforts and work that involves manipulating very cold atoms. They have also been found to play a roll in the development of colloidal clusters.

In this new work, the researchers were investigating the ways that light could be stopped from spreading—more specifically, ways that laser light could be trapped in a tight spot. To that end, they used a laser beam to stencil a special a type of crystal: a photorefractive strontium barium niobite crystal with nonlinear holographic properties. The stencil forced a beam of laser light to form into a twisted Moiré lattice. As the light moved through the lattice, the researchers found that solitons formed. They also found that they could adjust the threshold of the laser power by fine-tuning the angles of the twists in the lattice. Additionally, the formation of solitons in the lattices occurred with smooth transitions, from fully periodic geometries to aperiodic ones. The researchers also noted that such thresholds in their setup were quite low.

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