Physics News and Discussions

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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.

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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.

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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

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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.

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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.

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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

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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.

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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.

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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

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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.