Physics News and Discussions

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The ATLAS collaboration observes the electroweak production of two jets and a Z-boson pair
https://phys.org/news/2023-04-atlas-col ... -jets.html
by Ingrid Fadelli , Phys.org

The ATLAS collaboration, the large research consortium involved in analyzing data collected by the ATLAS particle collider at CERN, recently observed the electroweak production of two Z bosons and two jets. This crucial observation, presented in Nature Physics, could greatly contribute to the understanding of standard model (SM) particle physics.

The SM of particle physics is a well-established theory describing the building blocks and fundamental forces in the universe. This model describes weak bosons (i.e., bosons responsible for the so-called 'weak force') as mediators of the electroweak interaction.

The scattering of massive weak bosons, such as W and Z bosons, is constrained specifically to interactions, where the mediators themselves carry the charge of these interactions. This scattering, also known as vector-boson scattering (VBS), also involves a type of Feynman diagrams or vertices known (i.e., quartic gauge vertices) that physicists have so far been unable to experimentally probe through other physical processes.

"Quartic gauge vertices are a so far unconfirmed section of the SM, which is, however of central importance to the self-consistency of the model," Gabriela Navarro, part of the ATLAS collaboration, told Phys.org. "An example for this self-consistency is a delicate cancelation of scattering amplitudes involving Triple Gauge Vertices, Quartic Gauge Vertices and Vertices involving the Higgs Boson. A study of these processes is an independent and crucial test of the BEH-Mechanism for breaking the electroweak symmetry in the SM (EWSB)."

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Breakthrough in magnetic quantum material paves way for ultra-fast sustainable computers
https://phys.org/news/2023-04-breakthro ... paves.html
by Chalmers University of Technology

The discovery of new quantum materials with magnetic properties could pave the way for ultra-fast and considerably more energy-efficient computers and mobile devices. So far, these types of materials have been shown to work only in extremely cold temperatures. Now, a research team at Chalmers University of Technology in Sweden are the first to make a device made of a two-dimensional magnetic quantum material work in room temperature.

Today's rapid IT expansion generates enormous amounts of digital data that needs to be stored, processed, and communicated. This comes with an ever-increasing need for energy—projected to consume more than 30% of the world's total energy consumption by 2050. To combat the problem, the research community has entered a new paradigm in materials science. The research and development of two-dimensional quantum materials, that form in sheets and are only a few atoms thick, have opened new doors for sustainable, faster and more energy-efficient data storage and processing in computers and mobiles.

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Particle trio exceeds expectations at Large Hadron Collider
https://phys.org/news/2023-04-particle- ... adron.html
by Chris Patrick, SLAC National Accelerator Laboratory

The ATLAS experiment has confirmed that a trio of particles—a top-antitop quark pair and a W boson—occurs more frequently than expected in the wake of proton-proton collisions inside the Large Hadron Collider (LHC).

The process that creates these three particles post-impact is quite rare: Only one out of every 50,000 collisions at the LHC produces the trio, known as ttW. After popping into existence, top quarks and W bosons are short-lived and decay almost immediately, so the team identified ttW events based on the electrons and muons into which they decay.

Members of the ATLAS group at the Department of Energy's SLAC National Accelerator Laboratory have spent the last three years completing a complex analysis to measure the process, including developing novel methods to estimate and remove background and detector effects to maximize the accuracy and detail of the analysis of the measurement. The results will help researchers better test theories of elementary particle physics as well as help experimentalists studying other particle physics processes.

"The only measurements of ttW production come from the LHC—it is the first collider that can produce these types of events at a large enough rate to be measured," said Brendon Bullard, research associate at SLAC National Accelerator Laboratory and leader of this data analysis.
A puzzling excess

ATLAS first observed the ttW process in 2015 using data collected during the LHC's Run 1, which took place between 2010 and 2012. Subsequent measurements using a subset of data collected during Run 2 (2015-2018) suggested that ttW was cropping up more than predicted by the Standard Model of particle physics, which physicists use to describe the behavior of subatomic particles.

The most recent measurement using the full dataset collected by ATLAS during Run 2 has led to a more precise measurement of ttW, finding the total production rate to be about 20 percent higher than theoretical predictions. Fresh results from the CMS experiment corroborate this excess.

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[caltrek]

Scientists Find Link Between Photosynthesis and ‘Fifth State of Matter’
May 3, 2023

Introduction:

(Eurekalert) Inside a lab, scientists marvel at a strange state that forms when they cool down atoms to nearly absolute zero. Outside their window, trees gather sunlight and turn them into new leaves. The two seem unrelated—but a new study from the University of Chicago suggests that these processes aren’t so different as they might appear on the surface.

The study, published in PRX Energy on April 28, found links at the atomic level between photosynthesis and exciton condensates—a strange state of physics that allows energy to flow frictionlessly through a material. The finding is scientifically intriguing and may suggest new ways to think about designing electronics, the authors said.

“As far as we know, these areas have never been connected before, so we found this very compelling and exciting,” said study co-author Prof. David Mazziotti.

Mazziotti’s lab specializes in modelling the complicated interactions of atoms and molecules as they display interesting properties. There’s no way to see these interactions with the naked eye, so computer modeling can give scientists a window into why the behavior happens—and can also provide a foundation for designing future technology.

In particular, Mazziotti and study co-authors Anna Schouten and LeeAnn Sager-Smith have been modelling what happens at the molecular level when photosynthesis occurs.

Read more here: https://www.eurekalert.org/news-releases/988142

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Entangled quantum circuits further disprove Einstein's concept of local causality
https://phys.org/news/2023-05-entangled ... ncept.html
by Felix Würsten, ETH Zurich

A group of researchers led by Andreas Wallraff, Professor of Solid State Physics at ETH Zurich, has performed a loophole-free Bell test to disprove the concept of "local causality" formulated by Albert Einstein in response to quantum mechanics.

By showing that quantum mechanical objects that are far apart can be much more strongly correlated with each other than is possible in conventional systems, the researchers have provided further confirmation for quantum mechanics. What's special about this experiment is that the researchers were able for the first time to perform it using superconducting circuits, which are considered to be promising candidates for building powerful quantum computers.
An old dispute

A Bell test is based on an experimental setup that was initially devised as a thought experiment by British physicist John Bell in the 1960s. Bell wanted to settle a question that the greats of physics had already argued about in the 1930s: Are the predictions of quantum mechanics, which run completely counter to everyday intuition, correct, or do the conventional concepts of causality also apply in the atomic microcosm, as Albert Einstein believed?

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Supercomputing simulations spot electron orbital signatures
https://phys.org/news/2023-05-supercomp ... tures.html
by University of Texas at Austin

No one will ever be able to see a purely mathematical construct such as a perfect sphere. But now, scientists using supercomputer simulations and atomic resolution microscopes have imaged the signatures of electron orbitals, which are defined by mathematical equations of quantum mechanics and predict where an atom's electron is most likely to be.

Scientists at UT Austin, Princeton University, and ExxonMobil have directly observed the signatures of electron orbitals in two different transition-metal atoms, iron (Fe) and cobalt (Co) present in metal-phthalocyanines. Those signatures are apparent in the forces measured by atomic force microscopes, which often reflect the underlying orbitals and can be so interpreted.

Their study was published in March 2023 as an Editors' Highlight in the journal Nature Communications.

"Our collaborators at Princeton University found that despite Fe and Co being adjacent atoms on the periodic table, which implies similarity, the corresponding force spectra and their measured images show reproducible experimental differences," said study co-author James R. Chelikowsky, the W.A. "Tex" Moncrief, Jr. Chair of Computational Materials and professor in the Departments of Physics, Chemical Engineering, and Chemistry in the College of Natural Sciences at UT Austin. Chelikowsky also serves as the director of the Center for Computational Materials at the Oden Institute for Computational Engineering and Sciences.

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Telecom-wavelength quantum repeater node transmits quantum information over tens of kilometers
https://phys.org/news/2023-05-telecom-w ... -tens.html
by University of Innsbruck

A quarter century ago, theoretical physicists at the University of Innsbruck made the first proposal on how to transmit quantum information via quantum repeaters over long distances, which would open the door to the construction of a worldwide quantum information network.

Now, a new generation of Innsbruck researchers has built a quantum repeater node for the standard wavelength of telecommunication networks and transmitted quantum information over tens of kilometers. The study is published in the journal Physical Review Letters.

Quantum networks connect quantum processors or quantum sensors with each other. This allows tap-proof communication and high-performance distributed sensor networks. Between network nodes, quantum information is exchanged by photons that travel through optical waveguides. Over long distances, however, the likelihood of photons being lost increases dramatically.

As quantum information cannot simply be copied and amplified, 25 years ago Hans Briegel, Wolfgang Dür, Ignacio Cirac and Peter Zoller, then all at the University of Innsbruck, provided the blueprints for a quantum repeater. These featured light-matter entanglement sources and memories to create entanglement in independent network links that are connected between them by a so-called entanglement swap to finally distribute entanglement over long distances.
Even transmission over 800 kilometers possible

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Laser physicists directly observe first femtoseconds after photoinjection
https://phys.org/news/2023-05-laser-phy ... ction.html
by Ludwig Maximilian University of Munich

A laser pulse hits an electron in a solid. If it receives enough energy from the light wave, it can then move freely through a solid. This phenomenon, which scientists have been exploring since the beginnings of quantum mechanics, is called photoinjection. There are still open questions about how the relevant processes unfold in time.

Laser physicists of the attoworld team of LMU and the Max Planck Institute of Quantum Optics have now made a direct observation of how the optical properties of silicon and silicon dioxide evolve during the first few femtoseconds (millionths of a billionth of a second) after photoinjection with a strong laser pulse.

This physics of photoinjection is relatively simple when it comes to the photoelectric effect explained by Albert Einstein. Here, an electron absorbs a single photon that has enough energy to free the electron from a potential that constrains its motion. It gets more complicated when no photon in the light wave has enough energy to do so. In this case, bound electrons can become free by absorbing more than one photon at once or by quantum tunneling. These are nonlinear processes that are effective only when the electric field is strong, which means that only the central part of a laser pulse can drive them efficiently.

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First measurements of hypernuclei flow at the Relativistic Heavy Ion Collider
https://phys.org/news/2023-05-hypernucl ... lider.html
by Karen McNulty Walsh, Brookhaven National Laboratory

Physicists studying particle collisions at the Relativistic Heavy Ion Collider (RHIC) have published the first observation of directed flow of hypernuclei. These short-lived, rare nuclei contain at least one "hyperon" in addition to ordinary protons and neutrons.

Hyperons contain at least one "strange" quark in place of one of the up or down quarks that make up ordinary nucleons (the collective name for protons and neutrons). Such strange matter is thought to be abundant in the hearts of neutron stars, which are among the densest, most exotic objects in the universe. While blasting off to neutron stars to study this exotic matter is still the stuff of science fiction, particle collisions could give scientists insight into these celestial objects from a laboratory right here on Earth.

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The first experimental observation of subpicosecond electron bunches originating from an ultracold source
https://phys.org/news/2023-05-experimen ... acold.html
by Ingrid Fadelli , Phys.org

Identifying new sources that produce electrons faster could help to advance the many imaging techniques that rely on electrons. In a recent paper published in Physical Review Letters, a team of researchers at Eindhoven University of Technology demonstrated the scattering of subpicosecond electron bunches from an ultracold electron source.

"Our research group is working to develop the next generation of ultrafast electron sources to push imaging techniques such as ultrafast electron diffraction to the next level," Tim de Raadt, one of the researchers who carried out the study, told Phys.org.

"The idea of using laser-cooled ultracold gas clouds as an electron source to improve the state-of-the-art in brightness was first introduced in a paper published in 2005. Since then, research efforts have produced multiple versions of such a ultracold electron source, with the most recent one (used in this work) focusing on making the source compact, easy to align and operate, and being more stable, as described in another past paper that also studied the transverse electron beam properties."

The primary objective of the recent work by de Raadt and his colleagues was to further assess the performance of the type of compact laser cooled ultracold source identified in their previous work, particularly looking at its longitudinal beam properties. By better understanding the physics behind this source, they could optimize its performance and enable its use to advance imaging techniques.

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Experiments see first evidence of a rare Higgs boson decay
https://phys.org/news/2023-05-evidence- ... decay.html
by CERN

The discovery of the Higgs boson at CERN's Large Hadron Collider (LHC) in 2012 marked a significant milestone in particle physics. Since then, the ATLAS and CMS collaborations have been diligently investigating the properties of this unique particle and searching to establish the different ways in which it is produced and decays into other particles.

At the Large Hadron Collider Physics (LHCP) conference this week, ATLAS and CMS report how they teamed up to find the first evidence of the rare process in which the Higgs boson decays into a Z boson, the electrically neutral carrier of the weak force, and a photon, the carrier of the electromagnetic force. This Higgs boson decay could provide indirect evidence of the existence of particles beyond those predicted by the Standard Model of particle physics.

The decay of the Higgs boson into a Z boson and a photon is similar to that of a decay into two photons. In these processes, the Higgs boson does not decay directly into these pairs of particles. Instead, the decays proceed via an intermediate "loop" of "virtual" particles that pop in and out of existence and cannot be directly detected. These virtual particles could include new, as yet undiscovered particles that interact with the Higgs boson.

The Standard Model predicts that, if the Higgs boson has a mass of around 125 billion electronvolts, approximately 0.15% of Higgs bosons will decay into a Z boson and a photon. But some theories that extend the Standard Model predict a different decay rate. Measuring the decay rate therefore provides valuable insights into both physics beyond the Standard Model and the nature of the Higgs boson.

Previously, using data from proton–proton collisions at the LHC, ATLAS and CMS independently conducted extensive searches for the decay of the Higgs boson into a Z boson and a photon. Both searches used similar strategies, identifying the Z boson through its decays into pairs of electrons or muons—heavier versions of electrons. These Z boson decays occur in about 6.6% of the cases.

In these searches, collision events associated with this Higgs boson decay (the signal) would be identified as a narrow peak, over a smooth background of events, in the distribution of the combined mass of the decay products. To enhance the sensitivity to the decay, ATLAS and CMS exploited the most frequent modes in which the Higgs boson is produced and categorized events based on the characteristics of these production processes. They also used advanced machine-learning techniques to further distinguish between signal and background events.

[caltrek]

First Signs of Rare Higgs Boson Decay Discovered by Physicists
by Mike McCrae
May 29, 2023

Introduction:

(Science Alert)A refined hunt for the extremely rare transformation of the Higgs boson has delivered results, providing the first evidence of a process that could hint at unknown particles.

Reconciling the results of several years' worth of proton crashes inside two different detectors at the European Organization for Nuclear Research's (CERN) Large Hadron Collider (LHC), physicists bumped up the statistical precision of the rate at which the famous 'mass-giving' particle decayed into a photon and a Z boson. (See also previous article in this thread -caltrek)

The results, shared at the LHC Physics Conference in Belgrade last week, fall well short of what might be considered significant. But the process itself can be improved to hone in on the bubble and hiss of quantum recipes, and help determine where exotic new forces and building blocks might exist.

The Higgs particle became the darling of the physics world in 2012 when evidence of its existence was confirmed by the ATLAS (or 'A Toroidal LHC Apparatus') and CMS (Compact Muon Solenoid) detectors at CERN.

Not only was it the final entry in that grand map of particles – the Standard Model – to be experimentally confirmed; its observation promised to be a window into hidden parts of the quantum realm.

After a further brief review of the nature of Higgs particle, the article explains how it is hoped that continued effort will yield the discovery of new particles.

Read more here: https://www.sciencealert.com/first-sig ... ysicists

[wjfox]

Qubits 30 meters apart used to confirm Einstein was wrong about quantum

Experiment linked qubits using a supercold wire over 30 meters long.

JOHN TIMMER - 5/10/2023, 7:12 PM

A new experiment uses superconducting qubits to demonstrate that quantum mechanics violates what's called local realism by allowing two objects to behave as a single quantum system no matter how large the separation between them. The experiment wasn't the first to show that local realism isn't how the Universe works—it's not even the first to do so with qubits.

But it's the first to separate the qubits by enough distance to ensure that light isn't fast enough to travel between them while measurements are made. And it did so by cooling a 30-meter-long aluminum wire to just a few milliKelvin. Because the qubits are so easy to control, the experiment provides a new precision to these sorts of measurements. And the hardware setup may be essential for future quantum computing efforts.

Albert Einstein was famously uneasy with some of the consequences of quantum entanglement. If quantum mechanics were right, then a pair of entangled objects would behave as a single quantum system no matter how far apart the objects were. Altering the state of one of them should instantly alter the state of the second, with the change seemingly occurring faster than light could possibly travel between the two objects. This, Einstein argued, almost certainly had to be wrong.

https://arstechnica.com/science/2023/05 ... ity-local/



Credit: ETH Zurich / Daniel Winkler

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Quantum materials: Electron spin measured for the first time
https://phys.org/news/2023-06-quantum-m ... ctron.html
by Università di Bologna

An international research team has succeeded for the first time in measuring the electron spin in matter—i.e., the curvature of space in which electrons live and move—within "kagome materials," a new class of quantum materials.

The results obtained—published in Nature Physics—could revolutionize the way quantum materials are studied in the future, opening the door to new developments in quantum technologies, with possible applications in a variety of technological fields, from renewable energy to biomedicine, from electronics to quantum computers.

Success was achieved by an international collaboration of scientists, in which Domenico Di Sante, professor at the Department of Physics and Astronomy "Augusto Righi," participated for the University of Bologna as part of his Marie Curie BITMAP research project. He was joined by colleagues from CNR-IOM Trieste, Ca' Foscari University of Venice, University of Milan, University of Würzburg (Germany), University of St. Andrews (UK), Boston College and University of Santa Barbara (U.S.).

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Large Hadron Collider may be closing in on the universe's missing antimatter
By Keith Cooper published about 18 hours ago

'Through more precise measurements, large improvements have been made in our knowledge.'


Physicists at the Large Hadron Collider (LHC) are closing in on an explanation for why we live in a universe of matter and not antimatter.

Matter and antimatter are two sides of the same coin. Every type of particle has an anti-particle, which is its equal and opposite. For instance, the antimatter equivalent of a negatively charged electron is a positively charged positron.

The Standard Model of physics tells us that if we substitute a particle for its antiparticle, it should still operate within the laws of physics in the same way. As such, the Big Bang should not have had a preference for creating one type over another — this symmetry at the heart of nature means that matter and antimatter should have formed in equal amounts in the Big Bang.

Lucky for us, this does not seem to have been the case, because when you put matter and antimatter together, the outcome is explosive to say the least. Had matter and antimatter been crafted in equal amounts, then they would have annihilated each other, creating a cosmos filled with a sea of radiation, no atoms and no life. Today, the only antimatter is that which is produced in particle decays and interactions.

More:
https://www.space.com/large-hadron-coll ... tification

[wjfox]

Camera brings ‘unprecedented clarity’ to restoration of historic artworks

Mon 26 Jun 2023 08.02 BST

Scientists have developed technology that will revolutionise the restoration of historic works of art by allowing conservators to identify and remove ageing varnish with total accuracy.

A team at King’s College London’s department of physics has harnessed the power of fluorescence to bring “unprecedented clarity” to the conservation process, said Prof Klaus Suhling.

A revolutionary camera will allow experts to distinguish between varnish and other components in an artwork, such as paints and binders.

[...]

The King’s College team developed a 25,000-pixel photon sensitive camera that uses a technique called macroscopic fluorescence lifetime imaging (FLIM) to harness the natural fluorescence in centuries-old varnish.

Each pixel has a stopwatch that measures when the light from a surface enters it. “By comparing the fluorescence of the varnish to these other components, we can chart where varnish sits with a level of accuracy never previously achieved,” said Suhling.

https://www.theguardian.com/artanddesig ... c-artworks



Credit: National Trust Images/National Trust

[weatheriscool]

Researchers devise new quantum photonics technique to create better holograms
https://phys.org/news/2023-07-quantum-p ... grams.html
by University of Ottawa

By enabling the recording and reconstruction of faint light beams containing a single particle of light, a new technique opens the door to holographic imaging of remote objects.

Researchers from the University of Ottawa, the National Research Council of Canada(NRC) and Imperial College London have developed a new quantum-inspired technique to perform holography, the rendering of a three-dimensional image using lasers— just like in Star Trek and Star Wars.

Led byuOttawa's Dr. Benjamin Sussman, adjunct professor of physics in the Faculty of Science, the researchers collaborated at the uOttawa-NRC Joint Centre for Extreme Photonics to develop a pioneering quantum-inspired technique for holography. Their aim was to record and reconstruct extremely faint light beams, consisting of a mere single particle of light, known as a photon.

Their work has the potential to revolutionize 3D scene reconstruction and unlock a plethora of applications across diverse fields.

[weatheriscool]

Einstein's theory of relativity reaffirmed, despite doubts from quantum physicists
https://phys.org/news/2023-07-einstein- ... cists.html
by Leibniz University Hannover

One of the most basic assumptions of fundamental physics is that the different properties of mass—weight, inertia and gravitation—always remain the same in relation to each other. Without this equivalence, Einstein's theory of relativity would be contradicted and our current physics textbooks would have to be rewritten. Although all measurements to date confirm the equivalence principle, quantum theory postulates that there should be a violation.

This inconsistency between Einstein's gravitational theory and modern quantum theory is the reason why ever more precise tests of the equivalence principle are particularly important. A team from the Center of Applied Space Technology and Microgravity (ZARM) at University of Bremen, in collaboration with the Institute of Geodesy (IfE) at Leibniz University Hannover, has now succeeded in proving with 100 times greater accuracy that passive gravitational mass and active gravitational mass are always equivalent—regardless of the particular composition of the respective masses.

The research was conducted within the framework of the Cluster of Excellence "QuantumFrontiers." Today, the team published their findings as a highlights article in Physical Review Letters.

[caltrek]

New Synthetic Particles Move Like Hurricanes and Algae
by James Devitt
July 17, 2023

Introduction:

(Futurity) A new system uses laser beams and the spinning of microscopic rotors to replicate the movement of naturally occurring phenomena, such as hurricanes and algae.

The breakthrough, reported in the journal Nature Communications, reveals new ways that living matter can be reproduced on a cellular scale.

“Living organisms are made of materials that actively pump energy through their molecules, which produce a range of movements on a larger cellular scale,” explains Matan Yah Ben Zion, a doctoral student in New York University’s physics department at the time of the work and one of the paper’s authors. “By engineering cellular-scale machines from the ground up, our work can offer new insights into the complexity of the natural world.”
The research centers on vortical flows, which appear in both biological and meteorological systems, such as algae or hurricanes. Specifically, particles move into orbital motion in the flow generated by their own rotation, resulting in a range of complex interactions.

To better understand these dynamics, the paper’s authors, who also include Alvin Modin, an NYU undergraduate at the time of the study and now a doctoral student at Johns Hopkins University, and Paul Chaikin, an NYU physics professor, sought to replicate them at their most basic level. To do so, they created tiny micro-rotors—about 1/10th the width of a strand of human hair—to move micro-particles using a laser beam (Chaikin and his colleagues devised this process in a previous work).

The researchers found that the rotating particles mutually affected each other into orbital motion, with striking similarities to dynamics observed by other scientists in “dancing” algae—algae groupings that move in concert with each other.

Read more here: https://www.futurity.org/vortical-flow ... 944402-2