Physics News and Discussions

[weatheriscool]

PandaX sets new constraints on the search for light dark matter via ionization signals
https://phys.org/news/2023-07-pandax-co ... ation.html
by Ingrid Fadelli , Phys.org

Teams of physicists worldwide have been trying to detect dark matter, an elusive type of matter that does not emit, absorb, or reflect light. Due to its lack of interactions with electromagnetic forces, this matter is very difficult to observe directly, thus most researchers are instead searching for signals originating from its interactions with other particles in its surroundings.

The PandaX experiment is a research effort dedicated to the search of dark matter using data collected by the Particle and Astrophysical xenon detector, situated at the China Jinping Underground Laboratory (CJPL) in Sichuan, in China. In a recent paper published in Physical Review Letters, the researchers involved in this large-scale experiment published the results of their most recent search for light dark matter (i.e., weakly interacting massive particles with masses below 1 GeV).

[weatheriscool]

ATLAS sets record precision on Higgs boson's mass
https://phys.org/news/2023-07-atlas-pre ... -mass.html
by CERN

In the 11 years since its discovery at the Large Hadron Collider (LHC), the Higgs boson has become a central avenue for shedding light on the fundamental structure of the universe. Precise measurements of the properties of this special particle are among the most powerful tools physicists have to test the Standard Model, currently the theory that best describes the world of particles and their interactions. At the Lepton Photon Conference this week, the ATLAS collaboration reported how it has measured the mass of the Higgs boson more precisely than ever before.

The mass of the Higgs boson is not predicted by the Standard Model and must therefore be determined by experimental measurement. Its value governs the strengths of the interactions of the Higgs boson with the other elementary particles as well as with itself. A precise knowledge of this fundamental parameter is key to accurate theoretical calculations which, in turn, allow physicists to confront their measurements of the Higgs boson's properties with predictions from the Standard Model. Deviations from these predictions would signal the presence of new or unaccounted-for phenomena. The Higgs boson's mass is also a crucial parameter driving the evolution and the stability of the universe's vacuum.

The ATLAS and CMS collaborations have been making ever more precise measurements of the Higgs boson's mass since the particle's discovery. The new ATLAS measurement combines two results: a new Higgs boson mass measurement based on an analysis of the particle's decay into two high-energy photons (the "diphoton channel") and an earlier mass measurement based on a study of its decay into four leptons (the "four-lepton channel").

[weatheriscool]

Physicists achieve breakthrough in Monte Carlo computer simulations
https://phys.org/news/2023-07-physicist ... tions.html
by Leipzig University

Researchers at Leipzig University have developed a highly efficient method to investigate systems with long-range interactions that were previously puzzling to experts. These systems can be gases or even solid materials such as magnets whose atoms interact not only with their neighbors but also far beyond.

Professor Wolfhard Janke and his team of researchers use Monte Carlo computer simulations for this purpose. This stochastic process, named after the Monte Carlo casino, generates random system states from which the desired properties of the system can be determined. In this way, Monte Carlo simulations provide deep insights into the physics of phase transitions.

The researchers have developed a new algorithm that can perform these simulations in a matter of days, which would have taken centuries using conventional methods. They have published their new findings in the journal Physical Review X.

[weatheriscool]

New radar research overcomes nearly century-old trade-off between wavelength and distance resolution
https://phys.org/news/2023-08-radar-cen ... tance.html
by Chapman University

New interference radar functions employed by a team of researchers from Chapman University and other institutions improve the distance resolution between objects using radar waves. The results may have important ramifications in military, construction, archaeology, mineralogy and many other domains of radar applications.

This first proof-of-principle experiment opens a new area of research with many possible applications that can be disruptive to the multi-billion dollar radar industry. There are many new avenues to pursue both in theory and experiment.

The discovery addresses a nine decades-old problem that requires scientists and engineers to sacrifice detail and resolution for observation distance—underwater, underground, and in the air. The previous bound limited the distance estimated between objects to be one quarter of the wavelength of radio waves; this technology improves the distance resolution between objects using radar waves.

"We believe this work will open a host of new applications as well as improve existing technologies," says John Howell, the lead author of the article published today in Physical Review Letters. "The possibility of efficient humanitarian demining or performing high-resolution, non-invasive medical sensing is very motivating," he adds.

Howell and a team of researchers from the Institute for Quantum Studies at Chapman University, the Hebrew University of Jerusalem, the University of Rochester, the Perimeter Institute and the University of Waterloo have demonstrated range resolution more than 100 times better than the long-believed limit. This result breaks the trade-off between resolution and wavelength, allowing operators to use long wavelengths and now have high spatial resolution.

[weatheriscool]

Scientists observe first evidence of 'quantum superchemistry' in the laboratory

by Louise Lerner, University of Chicago
https://phys.org/news/2023-08-scientist ... atory.html

A team from the University of Chicago has announced the first evidence for "quantum superchemistry"—a phenomenon where particles in the same quantum state undergo collective accelerated reactions. The effect had been predicted, but never observed in the laboratory.

The findings, published July 24 in Nature Physics, open the door to a new field. Scientists are intensely interested in what are known as "quantum-enhanced" chemical reactions, which could have applications in quantum chemistry, quantum computing, and other technologies, as well as in better understanding the laws of the universe.

"What we saw lined up with the theoretical predictions," said Cheng Chin, a professor of physics and member of the James Franck Institute and Enrico Fermi Institute, whose lab conducted the research. "This has been a scientific goal for 20 years, so it's a very exciting era."

[weatheriscool]

Demon hunting: Physicists confirm 67-year-old prediction of massless, neutral composite particle
https://phys.org/news/2023-08-demon-phy ... utral.html
by Michael O'Boyle, University of Illinois Grainger College of Engineering

In 1956, theoretical physicist David Pines predicted that electrons in a solid can do something strange. While they normally have a mass and an electric charge, Pines asserted that they can combine to form a composite particle that is massless, neutral, and does not interact with light. He called this particle a "demon." Since then, it has been speculated to play an important role in the behaviors of a wide variety of metals. Unfortunately, the same properties that make it interesting have allowed it to elude detection since its prediction.

Now, a team of researchers led by Peter Abbamonte, a professor of physics at the University of Illinois Urbana-Champaign, have finally found Pines' demon 67 years after it was predicted. As the researchers report in the journal Nature, they used a nonstandard experimental technique that directly excites a material's electronic modes, allowing them to see the demon's signature in the metal strontium ruthenate.

[weatheriscool]

Scientists may be on brink of discovering fifth force of nature
Experts closing in on potentially identifying new force after surprise wobble of subatomic particle

Fri 11 Aug 2023 08.01 EDT

The tantalising theory that a fifth force of nature could exist has been given a boost thanks to unexpected wobbling by a subatomic particle, physicists have revealed.

According to current understanding, there are four fundamental forces in nature, three of which – the electromagnetic force and the strong and weak nuclear forces – are explained by the standard model of particle physics.

However, the model does not explain the other known fundamental force, gravity, or dark matter – a strange and mysterious substance thought to make up about 27% of the universe.

Now researchers have said there could be another, fifth, fundamental force of nature.

More: https://www.theguardian.com/science/202 ... rce-nature

[weatheriscool]

Switching 'spin' on and off (and up and down) in quantum materials at room temperature
https://phys.org/news/2023-08-quantum-m ... ature.html
by University of Cambridge

Researchers have found a way to control the interaction of light and quantum 'spin' in organic semiconductors, that works even at room temperature.

Spin is the term for the intrinsic angular momentum of electrons, which is referred to as up or down. Using the up/down spin states of electrons instead of the 0 and 1 in conventional computer logic could transform the way in which computers process information. And sensors based on quantum principles could vastly improve our abilities to measure and study the world around us.

An international team of researchers, led by the University of Cambridge, has found a way to use particles of light as a 'switch' that can connect and control the spin of electrons, making them behave like tiny magnets that could be used for quantum applications.

The researchers designed modular molecular units connected by tiny 'bridges.' Shining a light on these bridges allowed electrons on opposite ends of the structure to connect to each other by aligning their spin states. Even after the bridge was removed, the electrons stayed connected through their aligned spins.

[weatheriscool]

Research group detects a quantum entanglement wave for the first time using real-space measurements
https://phys.org/news/2023-08-group-qua ... space.html
by Aalto University

Triplons are tricky little things. Experimentally, they're exceedingly difficult to observe. And even then, researchers usually conduct the tests on macroscopic materials, in which measurements are expressed as an average across the whole sample.

That's where designer quantum materials offer a unique advantage, says Academy Research Fellow Robert Drost, the first author of a paper published in Physical Review Letters. These designer quantum materials let researchers create phenomena not found in natural compounds, ultimately enabling the realization of exotic quantum excitations.

"These materials are very complex. They give you very exciting physics, but the most exotic ones are also challenging to find and study. So, we are trying a different approach here by building an artificial material using individual components," says Professor Peter Liljeroth, head of the Atomic Scale physics research group at Aalto University.

Quantum materials are governed by the interactions between electrons at the microscopic level. These electronic correlations lead to unusual phenomena like high-temperature superconductivity or complex magnetic states, and quantum correlations give rise to new electronic states.

[weatheriscool]

New experimental research measures the speed of molecular charge migration for the first time
https://phys.org/news/2023-08-experimen ... ation.html
by SPIE

To discover how light interacts with molecules, the first step is to follow electron dynamics, which evolve at the attosecond timescale. The dynamics of this first step have been called charge migration (CM). CM plays a fundamental role in chemical reactions and biological functions associated with light–matter interaction. For years, visualizing CM at the natural timescale of electrons has been a formidable challenge in ultrafast science due to the ultrafine spatial (angstrom) and ultrafast temporal (attosecond) resolution required.

Experimentally, the sensitive dependence of CM on molecular orbitals and orientations has made the CM dynamics complex and difficult to trace. There are still some open questions about molecular CM that remain unclear. One of the most fundamental questions: how fast does the charge migrate in molecules? Although molecular CM has been extensively studied theoretically in the last decade by using time-dependent quantum chemistry packages, a real measurement of the CM speed has remained unattainable, due to the extreme challenge.

As reported in Advanced Photonics, a research team from Huazhong University of Science and Technology (HUST), in cooperation with theoretical teams from Kansas State University and University of Connecticut, recently proposed a high harmonic spectroscopy (HHS) method for measuring the CM speed in a carbon-chain molecule, butadiyne (C4H2).

[weatheriscool]

LHCb collaboration observes a doubly charged tetraquark and its neutral partner for the first time
https://phys.org/news/2023-09-lhcb-coll ... utral.html
by Ingrid Fadelli , Phys.org

The observation of elusive, exotic particles is the key objective of countless studies, as it could open new avenues for research, while also improving present knowledge of the matter contained in the universe and its underlying physics. The quark model, a theoretical model introduced in 1964, predicted the existence of elementary subatomic particles known as quarks in their different configurations.

Quarks and antiquarks (the anti-matter equivalent of quarks) are predicted to be constituents of various subatomic particles. These include "conventional" particles, such as mesons and baryons, as well as more complex particles made up of four or five quarks (i.e., tetraquarks and pentaquarks, respectively).

The Large Hadron Collider beauty (LHCb) experiment, a research effort involving a large group of researchers at different institutes worldwide, has been trying to observe some of these fascinating particles for over a decade, using data collected at CERN's LHC particle collider in Switzerland. In a recent paper published in Physical Review Letters, they reported the very first observation of a doubly charged tetraquark and its neutral partner.

[weatheriscool]

Researchers observe electron scattering from radioisotopes that do not occur naturally for the first time
https://phys.org/news/2023-09-electron- ... rally.html
by Bob Yirka , Phys.org

A team of chemists and physicists with members from Kyoto University, the Nishina Center for Accelerator-Based Science, RIKEN, Rikkyo University and Tohoku University, all in Japan, have for the first time observed electron scattering from radioisotopes that do not occur naturally. The study is published in the journal Physical Review Letters.

Ever since the discovery in the 1950s that atomic nuclei have a finite size—on the femtometer scale—researchers have been looking for ways to create pictures of atomic nuclei to learn more about their structure. Such a device would necessarily have to be a type of femtoscope. In this new effort, the research team built a system that represents the realization of such a device.

[weatheriscool]

Scientists demonstrate new, improved way to make infrared light, with quantum dots
https://phys.org/news/2023-09-scientist ... -dots.html
by Louise Lerner, University of Chicago

Scientists with the University of Chicago have demonstrated a way to create infrared light using colloidal quantum dots. The researchers said the method demonstrates great promise; the dots are already as efficient as existing conventional methods, even though the experiments are still in early stages.

The dots could someday form the basis of infrared lasers as well as small and cost-effective sensors, such as those used in exhaust emissions tests or breathalyzers.

"Right now the performance for these dots is close to existing commercial infrared light sources, and we have reason to believe we could significantly improve that," said Philippe Guyot-Sionnest, a professor of physics and chemistry at the University of Chicago, member of the James Frank Institute, and one of three authors on the paper published in Nature Photonics. "We're very excited for the possibilities."
The right wavelength

[weatheriscool]

Experimental quantum imaging distillation with undetected light
https://phys.org/news/2023-09-experimen ... ected.html
by Thamarasee Jeewandara , Phys.org

It is possible to image an object with an induced coherence effect by making use of photon pairs to gain information on the item of interest—without detecting the light probing it. While one photon illuminates the object, its partner alone is detected, thereby preventing the measurements of coincidence events to reveal information of the sought after object. This method can be made resilient to noise, as well.

In a new report published in Science Advances, Jorge Fuenzalida and a team in applied optics, precision engineering and theory communications in Germany experimentally showed how the method can be made resilient to noise. They introduced an imaging-distilled approach based on the interferometric modulation of the signal of interest to generate a high-quality image of an object regardless of the extreme noise levels surpassing the actual signal of interest.
Quantum imaging

Quantum imaging is a promising field that is emerging with valid advantages when compared to classical protocols. Researchers have demonstrated this method across different scenarios to work in the low-photon flux regime by making use of undetected probing photons for super-resolution imaging.

Scientists can also develop protocols in quantum imaging without a classical counterpart based on quantum interference and entanglement. Quantum imaging protocols can, however, be made resilient to noise. For instance, distillation or purification can remove decoherence introduced by the environment in a quantum system.

It is also possible to implement quantum imaging distillation with one and several photon pair degrees of freedom. In this work, Fuenzalida and team introduced and experimentally verified a quantum imaging distillation method to detect single photons only.

[weatheriscool]

Impossible' millimeter wave sensor has wide potential
https://techxplore.com/news/2023-10-imp ... ntial.html
by Matt Marcure, UC Davis

Researchers at the University of California, Davis, have developed a proof-of-concept sensor that may usher in a new era for millimeter wave radars. In fact, they call its design a "mission impossible" made possible.

Millimeter wave radars send fast-moving electromagnetic waves to targets to analyze their movement, position and speed from the waves bounced back. The benefits of millimeter waves are their natural sensitivity to small-scale movements and their ability to focus on and sense data from microscopic objects.

The new sensor uses an innovative millimeter wave radar design to detect vibrations a thousand times smaller—and changes in a target's position one hundred times smaller—than a strand of human hair, making it better or on par with the world's most accurate sensors. Yet unlike its peers, this one is the size of a sesame seed, is cheap to produce and features a long battery life.

[wjfox]

Nobel Prize in Physics awarded to team behind short light pulses used to see processes inside atoms

03/10/2023

This year's Nobel Prize in Physics has been awarded to Pierre Agostini, Ferenc Krausz and Anne L'Huillier for their work on "experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter."

Their experiments "have given humanity new tools for exploring the world of electrons inside atoms and molecules," the Royal Swedish Academy of Sciences said as it announced the prize on Wednesday.

The three newly-minted Nobel Laureates have "demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes in which electrons move or change energy," the Academy said.

https://www.euronews.com/next/2023/10/0 ... cesses-ins

[weatheriscool]

Scientists develop a semi-device independent, randomness-free test for quantum correlation
https://phys.org/news/2023-10-scientist ... antum.html
by Tejasri Gururaj , Phys.org

In a new Physical Review Letters study, scientists have successfully presented a proof of concept to demonstrate a randomness-free test for quantum correlations and non-projective measurements, offering a groundbreaking alternative to traditional quantum tests that rely on random inputs.

"Quantum correlation" is a fundamental phenomenon in quantum mechanics and one that is central to quantum applications like communication, cryptography, computing, and information processing.

Bell's inequality, or Bell's theory, named after physicist John Stewart Bell, is the standard test used to determine the nature of correlation. However, one of the challenges with using Bell's theorem is the requirement of seed randomness for selecting measurement settings.

[weatheriscool]

Theoretical physicists present significantly improved calculation of the proton radius
https://phys.org/news/2023-10-theoretic ... adius.html
by Renée Dillinger-Reiter, Johannes Gutenberg University Mainz

A group of theoretical physicists at Johannes Gutenberg University Mainz (JGU) has once again succeeded in significantly improving their calculations of the electric charge radius of the proton published in 2021. For the first time they obtained a sufficiently precise result completely without the use of experimental data.

With respect to the size of the proton, these new calculations also favor the smaller value. Concurrently, the physicists for the first time have published a stable theory prediction for the magnetic charge radius of the proton. All new findings can be found in three preprints published on the arXiv server.

All known atomic nuclei consist of protons and neutrons, yet many of the characteristics of these ubiquitous nucleons remain to be understood. Specifically, despite several years of effort, scientists have been unable to pin down the radius of the proton. In 2010, the result of a new proton radius measurement technique involving laser spectroscopy of muonic hydrogen caused a stir—in this 'special' kind of hydrogen, the electron in the shell of the atom was replaced by its heavier relative, the muon, which is a much more sensitive probe for the proton's size.

The experimentalists came up with a significantly smaller value than that found following corresponding measurements of 'normal' hydrogen as well as the traditional method of determining the proton radius using electron-proton scattering. The big question that physicists have been asking ever since is whether this deviation could be evidence for new physics beyond the Standard Model or 'simply' reflects systematic uncertainties inherent to the different measuring methods.

[caltrek]

Asteroids May Be Hiding Never-Seen Elements from Beyond the Periodic Table
by Michele Starr
October 11, 2023

Introduction:

(Science Alert) The densest naturally occurring element on the periodic table is the metal osmium. At room temperature, it forms a solid with a density of 22.59 grams per cubic centimeter – nearly twice as dense as Earth's inner core and almost as dense as the core of Jupiter.

But there are some objects out there in the Solar System that seem to be way more dense than osmium; not even planetary cores, but asteroids, which don't have the mass to compress minerals into an ultradense state.

This has led scientists to speculate that there are naturally occurring, stable elements out there beyond the periodic table – even beyond the unstable, radioactive superheavy elements between atomic numbers 105 and 118, which have only ever been observed in laboratory settings.

It's unknown whether elements with more than 118 protons would even be stable – they've certainly never been observed, either in the wild or in laboratory settings. But theoretical work suggests that there's an island of stability around atomic number 164, where superheavy elements eould not be as prone to radioactive decay and may stick around, at least for a time.

Because these heavier elements are expected to be denser, they could explain peculiar observations involving the asteroid 33 Polyhymnia, a rock in the asteroid belt that measures roughly 50 to 60 kilometers (around 30 to 36 miles) across. One measurement has derived a density for 33 Polyhymnia of 75.28 grams per cubic centimeter, classifying it as a potential compact ultradense object (CUDO).

Read more here: https://www.sciencealert.com/asteroids ... c-table

[weatheriscool]

Working towards programmable matter: Unexpected behavior discovered in active particles
https://phys.org/news/2023-10-programma ... icles.html
by University of Münster

Investigating systems consisting of self-propelled particles—so-called active particles—is a rapidly growing area of research. In theoretical models for active particles, it is often assumed that the particles' swimming speed is always the same. This is not so, however, for particles produced in many experiments, for example for those propelled by ultrasound for medical applications. In these cases, the propulsion speed depends on the orientation.