Physics News and Discussions

weatheriscool
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Borexino gathers the first directional measurement of sub-MeV solar neutrinos using a monolithic scintillation detector
https://phys.org/news/2022-03-borexino- ... ithic.html
by Ingrid Fadelli , Phys.org

Borexino is a large-scale particle physics experiment that collected data until October 2021. Its key mission was to study low energy (sub-MeV) solar neutrinos using the Borexino detector, the world's most radio-pure liquid scintillator calorimeter, located at the Laboratori Nazionali del Gran Sasso near Aquila, in Italy.

The Borexino Collaboration, the research team conducting the experiment, recently gathered the first experimental measurement of sub-MeV solar neutrinos using a scintillation detector. This measurement, presented in a paper published in Physical Review Letters, could open new possibilities for the hybrid reconstruction of particle physics events using Cherenkov and scintillation signatures simultaneously.

"The main idea behind this work was to gather experimental proof that it is possible to use the information given by the Cherenkov photons even in a monolithic scintillation detector," Johann Martyn, one of the researchers who carried out the study, told Phys.org.

Currently, there are two main types of detectors for studying neutrinos, namely water Cherenkov detectors, such as the Super-Kamiokande (SNO) detector and liquid scintillator detectors, such as the Borexino detector. In water Cherenkov detectors, neutrinos scatter off electrons in the medium. If these electrons are moving faster than the speed of light in the water, they produce Cherenkov radiation.
weatheriscool
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Research places new limits on the bizarre behavior of neutrinos

by Adam Becker, Lawrence Berkeley National Laboratory
https://phys.org/news/2022-04-limits-bi ... rinos.html
In a laboratory under a mountain, physicists are using crystals far colder than frozen air to study ghostly particles, hoping to learn secrets from the beginning of the universe. Researchers at the Cryogenic Underground Observatory for Rare Events (CUORE) announced this week that they had placed some of the most stringent limits yet on the strange possibility that the neutrino is its own antiparticle. Neutrinos are deeply unusual particles, so ethereal and so ubiquitous that they regularly pass through our bodies without us noticing. CUORE has spent the last three years patiently waiting to see evidence of a distinctive nuclear decay process, only possible if neutrinos and antineutrinos are the same particle. CUORE's new data shows that this decay doesn't happen for trillions of trillions of years, if it happens at all. CUORE's limits on the behavior of these tiny phantoms are a crucial part of the search for the next breakthrough in particle and nuclear physics—and the search for our own origins.

"Ultimately, we are trying to understand matter creation," said Carlo Bucci, researcher at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy and the spokesperson for CUORE. "We're looking for a process that violates a fundamental symmetry of nature," added Roger Huang, a postdoctoral researcher at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and one of the lead authors of the new study.

CUORE—Italian for "heart"—is among the most sensitive neutrino experiments in the world. The new results from CUORE are based on a data set ten times larger than any other high-resolution search, collected over the last three years. CUORE is operated by an international research collaboration, led by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy and Berkeley Lab in the US. The CUORE detector itself is located under nearly a mile of solid rock at LNGS, a facility of the INFN. U.S. Department of Energy-supported nuclear physicists play a leading scientific and technical role in this experiment. CUORE's new results were published today in Nature.
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The most precise-ever measurement of W boson mass suggests the standard model needs improvement
https://phys.org/news/2022-04-precise-e ... ndard.html
by Fermi National Accelerator Laboratory
After 10 years of careful analysis and scrutiny, scientists of the CDF collaboration at the U.S. Department of Energy's Fermi National Accelerator Laboratory announced today that they have achieved the most precise measurement to date of the mass of the W boson, one of nature's force-carrying particles. Using data collected by the Collider Detector at Fermilab, or CDF, scientists have now determined the particle's mass with a precision of 0.01%—twice as precise as the previous best measurement. It corresponds to measuring the weight of an 800-pound gorilla to 1.5 ounces.

The new precision measurement, published in the journal Science, allows scientists to test the standard model of particle physics, the theoretical framework that describes nature at its most fundamental level. The result: The new mass value shows tension with the value scientists obtain using experimental and theoretical inputs in the context of the standard model.
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Researchers engineer electrically tunable graphene devices to study rare physics
https://phys.org/news/2022-04-electrica ... -rare.html
by University of Manchester

An international team, co-led by researchers at The University of Manchester's National Graphene Institute (NGI) in the UK and the Penn State College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points. The team published their results today in Science.

The work could advance optoelectronic technologies to better generate, control and sense light and potentially communications, according to the researchers. They demonstrated a way to control THz waves, which exist at frequencies between those of microwaves and infrared waves. The feat could contribute to the development of 'beyond-5G' wireless technology for high-speed communication networks.

Weak and strong interactions

Light and matter can couple, interacting at different levels: weakly, where they might be correlated but do not change each other's constituents; or strongly, where their interactions can fundamentally change the system. The ability to control how the coupling shifts from weak to strong and back again has been a major challenge to advancing optoelectronic devices—a challenge researchers have now solved.

"We have demonstrated a new class of optoelectronic devices using concepts of topology—a branch of mathematics studying properties of geometric objects," said co-corresponding author Coskun Kocabas, professor of 2D device materials at The University of Manchester. "Using exceptional point singularities, we show that topological concepts can be used to engineer optoelectronic devices that enable new ways to manipulate terahertz light."
weatheriscool
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Homing in on the Higgs boson interaction with the charm quark
https://phys.org/news/2022-03-homing-hi ... charm.html
by Ana Lopes, CERN
Since the discovery of the Higgs boson a decade ago, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) have been hard at work trying to unlock the secrets of this special particle. In particular, the collaborations have been investigating in detail how the Higgs boson interacts with fundamental particles such as the particles that make up matter, quarks and leptons. In the Standard Model of particle physics, these matter particles fall into three "generations" of increasing mass, and the Higgs boson interacts with them with a strength that is proportional to their mass. Any deviation from this behavior would provide a clear indication of new phenomena.
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caltrek
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W Boson Apparently More Massive than Expected – a Physicist Explains What it Means for the Standard Model
by Jhon Conway
April 13, 2022

https://theconversation.com/a-decade-of ... del-181028

Introduction:
(The Conversation) “You can do it quickly, you can do it cheaply, or you can do it right. We did it right.” These were some of the opening remarks from David Toback, leader of the Collider Detector at Fermilab, as he announced the results of a decadelong experiment to measure the mass of a particle called the W boson.

I am a high energy particle physicist, and I am part of the team of hundreds of scientists that built and ran the Collider Detector at Fermilab in Illinois – known as CDF.

After trillions of collisions and years of data collection and number crunching, the CDF team found that the W boson has slightly more mass than expected. Though the discrepancy is tiny, the results, described in a paper published in Science on April 7, 2022, have electrified the particle physics world. If the measurement is correct, it is yet another strong signal that there are missing pieces to the physics puzzle of how the universe works.
Conclusion:
Even before this measurement, some theorists had proposed potential new particles or forces that would result in the observed deviation. In the coming months and years, I expect a raft of new papers seeking to explain the puzzling mass of W bosons.

As a particle physicist, I am confident in saying that there must be more physics waiting to be discovered beyond the Standard Model. If this new result holds up, it will be the latest in a series of findings showing that the Standard Model and real-world measurements often don’t quite match. It is these mysteries that give physicists new clues and new reasons to keep searching for fuller understanding of matter, energy, space and time.
Don't mourn, organize.

-Joe Hill
weatheriscool
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Observation of the branched flow of spatially incoherent light in dish soap
https://phys.org/news/2022-04-spatially ... -soap.html
by Bob Yirka , Phys.org
A team of researchers at Technion-Israel Institute of Technology has conducted the first experimental observation of the branched flow of spatially incoherent light—in this case, using liquid dish soap. In their paper published in the journal Physical Review X, the group describes their experiments involving shining light on 2D samples of liquid dish soap and their observations.

Prior research has shown that light moving through a disordered media can lead to branching, where some amount of a beam can take one path around an object while another part of the same beam can take another path. Such branching can lead to channels of light moving through a given medium. In this new effort, the researchers used liquid dish soap as the medium.
weatheriscool
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Research team measures the mass of the top quark with unparalleled accuracy
https://phys.org/news/2022-04-team-mass ... uracy.html
by CERN
The CMS collaboration at the Large Hadron Collider (LHC) has performed the most accurate ever measurement of the mass of the top quark—the heaviest known elementary particle. The latest CMS result estimates the value of the top-quark mass with an accuracy of about 0.22%. The substantial gain in accuracy comes from new analysis methods and improved procedures to consistently and simultaneously treat different uncertainties in the measurement.

The precise knowledge of the top-quark mass is of paramount importance to understand our world at the smallest scale. Knowing this heaviest elementary particle as intimately as possible is crucial because it allows testing of the internal consistency of the mathematical description of all elementary particles, called the Standard Model.

For example, if the masses of the W boson and Higgs boson are known accurately, the top-quark mass can be predicted by the Standard Model. Likewise, using the top-quark and Higgs-boson masses, the W-boson mass can be predicted. Interestingly, despite much progress, the theoretical-physics definition of mass, which has to do with the effect of quantum-physics corrections, is still tough to pin down for the top quark.
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Lab creates superfluid circuit using fermions to study electron behavior
https://phys.org/news/2022-04-lab-super ... ctron.html
by Dartmouth College
Researchers at Dartmouth College have built the world's first superfluid circuit that uses pairs of ultracold electron-like atoms, according to a study published in Physical Review Letters.

The laboratory test bed gives physicists control over the strength of interactions between atoms, providing a new way to explore the phenomena behind exotic materials such as superconductors.

"Much of modern technology revolves around controlling the flow of electrons around circuits," said Kevin Wright, assistant professor of physics at Dartmouth and senior researcher of the study. "By using electron-like atoms we can test theories in ways that were not possible before."

While conductive materials such as copper are well understood, researchers do not completely understand how electrons move or can be controlled in exotic materials like topological insulators and superconductors that can be useful for building quantum computers.
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Scientists turn a hydrogen molecule into a quantum sensor
https://phys.org/news/2022-04-scientist ... ensor.html
by Brian Bell, University of California, Irvine
Physicists at the University of California, Irvine have demonstrated the use of a hydrogen molecule as a quantum sensor in a terahertz laser-equipped scanning tunneling microscope, a technique that can measure the chemical properties of materials at unprecedented time and spatial resolutions.

This new technique can also be applied to analysis of two-dimensional materials which have the potential to play a role in advanced energy systems, electronics and quantum computers.

Today in Science, the researchers in UCI's Department of Physics & Astronomy and Department of Chemistry describe how they positioned two bound atoms of hydrogen in between the silver tip of the STM and a sample composed of a flat copper surface arrayed with small islands of copper nitride. With pulses of the laser lasting trillionths of a second, the scientists were able to excite the hydrogen molecule and detect changes in its quantum states at cryogenic temperatures and in the ultrahigh vacuum environment of the instrument, rendering atomic-scale, time-lapsed images of the sample.

"This project represents an advance in both the measurement technique and the scientific question the approach allowed us to explore," said co-author Wilson Ho, Bren Professor of physics & astronomy and chemistry. "A quantum microscope that relies on probing the coherent superposition of states in a two-level system is much more sensitive than existing instruments that are not based on this quantum physics principle."
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