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Category: particle physics – Page 2

LHC’s first oxygen collisions signs of small-scale quark-gluon plasma

CMS scientists study the first-ever oxygen-oxygen collisions at the LHC, and observe signs of quarks and gluons losing energy when they travel through quark-gluon plasma – a state that existed just after the Big Bang.

When heavy ions such as lead (Pb) collide at nearly the speed of light inside the Large Hadron Collider (LHC), extreme conditions are created that can “melt” ordinary nuclear matter into a new state called the quark-gluon plasma (QGP). This hot and dense medium is believed to resemble the universe just microseconds after the Big Bang, when quarks and gluons – the fundamental building blocks of protons and neutrons – moved freely.

Physicists study the QGP medium by looking at how fast-moving quarks and gluons – collectively called partons – behave as they pass through it. Fast moving partons form sprays of particles, which can be seen as “jets” in particle detectors. In collisions of very small systems, such as proton-proton collisions, the observed jets are seen to retain the full energy or the original partons. In contrast, in heavy-ion collisions, the presence of the QGP medium leads to a significant loss of energy.

Measuring the quantum W state: Seeing a trio of entangled photons in one go

The concept of quantum entanglement is emblematic of the gap between classical and quantum physics. Referring to a situation in which it is impossible to describe the physics of each photon separately, this key characteristic of quantum mechanics defies the classical expectation that each particle should have a reality of its own, which gravely concerned Einstein.

Understanding the potential of this concept is essential for the realization of powerful new quantum technologies.

Developing such technologies will require the ability to freely generate a multi– quantum , and then to efficiently identify what kind of entangled state is present. However, when performing conventional quantum tomography, a method commonly used for state estimation, the number of measurements required grows exponentially with the number of photons, posing a significant data collection problem.

New quantum sensors can withstand extreme pressure

The world of quantum physics is already mysterious, but what happens when that strange realm of subatomic particles is put under immense pressure? Observing quantum effects under pressure has proven difficult for a simple reason: Designing sensors that can withstand extreme forces is challenging.

In a significant advance, a team led by physicists at WashU has created in an unbreakable sheet of crystallized . The sensors can measure stress and magnetism in materials under pressure that exceeds 30,000 times the pressure of the atmosphere.

“We’re the first ones to develop this sort of high-pressure sensor,” said Chong Zu, an assistant professor of physics in Arts & Sciences and a member of Washington University in St. Louis’ Center for Quantum Leaps. “It could have a wide range of applications in fields ranging from quantum technology, , to astronomy and geology.”

Synthetic magnetic fields steer light on a chip for faster communications

Electrons in a magnetic field can display striking behaviors, from the formation of discrete energy levels to the quantum Hall effect. These discoveries have shaped our understanding of quantum materials and topological phases of matter. Light, however, is made of neutral particles and does not naturally respond to magnetic fields in the same way. This has limited the ability of researchers to reproduce such effects in optical systems, particularly at the high frequencies used in modern communications.

To address this challenge, researchers from Shanghai Jiao Tong University and Sun Yat-Sen University have developed a method for generating pseudomagnetic fields—synthetic fields that mimic the influence of real magnetic fields—inside nanostructured materials known as photonic crystals.

Unlike previous demonstrations, which focused on specific effects such as photonic Landau levels, the new approach allows arbitrary control of how light flows within the material. Their research is published in Advanced Photonics.

Microscopes can now watch materials go quantum with liquid helium

A new specimen holder gives scientists more control over ultra-cold temperatures, enabling the study of how materials acquire properties useful in quantum computers.

Scientists can now reliably chill specimens near absolute zero for over 10 hours while taking images resolved to the level of individual atoms with an . The new capability comes from a liquid-helium-cooled sample holder designed by a team of scientists and engineers at the University of Michigan and Harvard University.

Conventional instruments can usually maintain such an extreme temperature, about-423 degrees Fahrenheit or 20 degrees above absolute zero, for a few minutes, capping out at a few hours. But longer periods of time are needed to take atomic-resolution images of candidate materials for advanced technologies.

Atom-thin crystals provide new way to power the future of computer memory

Picture the smartphone in your pocket, the data centers powering artificial intelligence, or the wearable health monitors that track your heartbeat. All of them rely on energy-hungry memory chips to store and process information. As demand for computing resources continues to soar, so does the need for memory devices that are smaller, faster, and far more efficient.

A new study by Auburn physicists has taken an important step toward meeting this challenge.

The study, “Electrode-Assisted Switching in Memristors Based on Single-Crystal Transition Metal Dichalcogenides,” published in ACS Applied Materials & Interfaces, shows how memristors—ultra-thin that “remember” past —switch their state with the help of electrodes and subtle atomic changes inside the material.

Atomic-level engineering enables new alloys that won’t break in extreme cold

Navigating the extreme cold of deep space or handling super-chilled liquid fuels here on Earth requires materials that won’t break. Most metals become brittle and fracture at such low temperatures. However, new research is pioneering an approach to build metal structures atom by atom to create tough and durable alloys that can withstand such harsh environments.

Traditional strengthening approaches are often not good enough for these applications. For example, a common heat treatment technique called precipitation hardening strengthens metals by creating tiny hard particles within their structure. But in , the materials can lose their ductility (the ability to bend, stretch or be pulled into a new shape without breaking) and fracture suddenly.

A study published in the journal Nature describes a new way to design so they stay strong and tough even at super low temperatures. The big idea is to create an alloy with two different types of perfectly arranged atomic structures inside it. These structures are called subnanoscale short-range ordering (SRO), which are tiny islands of organized atoms and nanoscale long-range ordering (NLRO), which are slightly larger.

Uniting the light spectrum on a single microchip

Focused laser-like light that covers a wide range of frequencies is highly desirable for many scientific studies and for many applications, for instance, quality control of manufacturing semiconductor electronic chips. But creating such broadband and coherent light has been difficult to achieve with anything but bulky, energy-hungry tabletop devices.

Now, a Caltech team led by Alireza Marandi, a professor of electrical engineering and applied physics at Caltech, has created a tiny device capable of producing an unusually wide range of laser-light frequencies with ultra-high efficiency—all on a microchip. The work has potential in areas ranging from communications and imaging to spectroscopy, where the light would aid the detection of atoms and molecules in various settings.

The researchers describe the new nanophotonic device and approach in a paper that appears in the journal Nature Photonics. The lead author of the paper, “Multi-Octave Frequency Comb from an Ultra-Low-Threshold Nanophotonic Parametric Oscillator,” is Ryoto Sekine (Ph. D.), who completed the work while a graduate student in Marandi’s lab.

Probing the Higgs Mechanism with Particle Collisions and AI

A deep neural network has proven essential in confirming a key prediction of one of the standard model’s cornerstones.

The Higgs mechanism explains why the electromagnetic and weak interactions have such drastically different strengths—that is, how their symmetry became broken a picosecond after the big bang. The Higgs does not interact with photons, rendering them massless, whereas they do interact with the carriers of the weak interaction (the W+, W–, and Z bosons), giving them masses of order 100 GeV. Their nonzero masses allow them to acquire a longitudinal polarization—that is, a spin orientation perpendicular to their direction of motion. Because of special relativity, photons and other massless bosons that travel at the speed of light can’t have longitudinal polarization, but the W and Z bosons and other massive particles can. If electroweak symmetry had been broken not by the Higgs mechanism but by a different interaction, there would be no Higgs boson to find.

A new view of the proton and its excited states

The small but ubiquitous proton serves as a foundation for the bulk of the visible matter in the universe. It abides at the very heart of matter, giving rise to everything we see around us as it anchors the nuclei of atoms. Yet, its structure is amazingly complex, and the quest to understand these details has occupied theorists and experimenters alike since its discovery over a century ago.

“A large part of the visible matter in the universe is made of protons,” said Kyungseon Joo, a physics professor at the University of Connecticut. “And so, if you want to understand the universe, it is important to understand the .”

Currently, proton structure is only well understood in processes where they are probed at high energy and where a lot of momentum is transferred to the proton. In such cases, the probes interact with the quarks and gluons (together called “partons”) that form the proton so quickly that they react like a tightly set rack of billiard balls hit by a well-struck cue ball.

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