In a recent paper in Nature Physics, an international research collaboration, including Edward G. Bilpuch Distinguished Professor Robert Janssens as a co-PI for the experiment, used world-class instrumentation at the Facility for Rare Isotope Beams (FRIB) to study the rare isotope chromium-62. Researchers used a gamma-ray spectroscopy experiment in tandem with theoretical models to identify an unexpected variety of shapes in chromium-62. The finding provides more insight into islands of inversion. (Graphic courtesy of the Facility for Rare Isotope Beams)
Increasing the bandwidth of existing optical fiber networks is vital as society’s appetite for information grows. Writing in npj Spintronics, an editorial article (titled ‘Communicating with magnons’: https://www.nature.com/articles/s44306-024-00060-1) highlighted a recent publication by Y. Xiong et al from Wei Zhang’s group (https://www.nature.com/articles/s44306-024-00012-9), where the team reported a new magnonic phenomena for further increasing the information capacity of a hybrid magnon-photon system, termed “opto-electro-magnonic oscillator”.
Congratulations to Prof. Brad Barlow who was recently awarded a 2024-2025 Faculty Research Grant from the NC Space Grant! This funding will support Barlow and several undergraduate students as they use optical photometry from space- and ground-based observatories to search for and characterize new spider binaries.
“Spider binaries are a class of compact binaries that typically consist of a pulsar (a highly magnetized, rotating neutron star) and a low-mass companion. The intense, high-energy radiation and wind from the neutron star slowly heats up and ablates material from the companion. In time, the orbital period will shorten, and the companion will be consumed. Studies of spider binaries can provide valuable insights into various astrophysical processes, including mass transfer and evolution, the properties and behavior of neutron stars, and high–energy electromagnetic emissions. Such systems are rare, and most have been discovered through X-ray/gamma-ray detections or radio observations of their millisecond pulsars. Due to a series of serendipitous events, Barlow’s research group has discovered one of the closest (and thus brightest) spider binaries currently known using optical photometry instead of radio or high-energy observations. This discovery was made while investigating high signal-to-noise light curves of hot subdwarf binaries — an unrelated type of binary. As the highly irradiated hot spot on the companion rotates in and out of view, the optical flux can vary by up to a factor of ~10 with a light curve shape that mimics those of hot subdwarf reflection effect binaries. Here Barlow’s team proposes a series of optical search strategies to uncover and study new spider binaries using data from NASA’s TESS spacecraft, the 4.1-m SOAR telescope, and Skynet.
Barlow’s hope is that student participation in this project will foster enthusiasm, collaboration, and a deeper understanding of the subject matter in student researchers. Students will learn how to search and review the astronomical literature on spider binaries and related objects; write basic Python scripts for data analysis and visualization; use TOPCAT to inspect and manipulate tabular data; download TESS photometry from the Barbara A. Mikulski Archive for Space Telescopes; compute Lomb Scargle periodograms to search for periodic signals in time-series data; obtain, reduce, and analyze time-series photometry from the Skynet telescope network; obtain, reduce, and analyze time-series spectroscopy from SOAR/Goodman; write clear and concise reports summarizing research results and progress; and give engaging and effective scientific presentations to the public and scientific audiences.”
Profs Otto Zhou and Jianping Lu, along with Prof. Yueh Lee, Radiology and Adjunct Prof of Physics and colleagues from computer sciences and data sciences and school of medicine, won one of the five Carolina Creativity Hubs award. The title of the project is:
“Advanced Medical Screening in Underserved Populations Using a Transportable Nanotube-Enabled Imaging System”
The project is based on the nanotube x-ray technology invented in our department.
The study is based on observations seen from the distant
vantage point of New Horizons, the spacecraft that flew past Pluto in 2015. At a distance of 59 astronomical units from the Sun (59 times the Sun’s orbit) the
cameras aboard the mission are not confused by radiation from gas and dust in
the inner solar system. They can see the light from the outer portions of our Galaxy
and the radiation emitted by galaxies billions of light years away.
The group finds that the diffuse optical light in the universe is consistent with the integrated
radiation from distant galaxies down to 30th magnitude, as seen in the Hubble Space
Telescope deep fields. That emission is 25 magnitudes fainter than the dimmest stars
visible to the human eye; ten billion times fainter than the dim stars seen in the sky.
Other key points from the study:
– New Horizons is 59 times farther out in the solar system than Earth’s orbit.
(that’s 5.5 billion miles, or light-travel travel time of 8 hrs 10 min)
– The faraway galaxies that contribute to the cosmic optical background emitted
their light many billions of years in the past.
Image: Map revealing the regions in space, marked by circles and triangles, where New Horizons measured the cosmic optical background. The team pointed the spacecraft’s LORRI instrument above and below the plane of the Milky Way Galaxy, along the map’s equator, to avoid light from the galaxy. (Credit: Postman et al., 2024, The Astrophysical Journal)
Prof. Wei Zhang joins forces in uplifting quantum sciences research and education across NC Triangle and Triad (NCAT).
A recent NSF grant under the NSF QISE interdisciplinary program may help build quantum connections across the NC Triangle (UNC) and Triad (NCAT) regime. The project aims to engineer tailored modes in hybrid magnonics for quantum signal transduction and communication. The research activities will be also complemented by rich outreach activities to engage with students from local high schools and community colleges, and dissemination plans to share the research findings with the public research community.
For more information regarding “magnonics”: please find “The 2024 magnonics roadmap”, J. Phys.: Condens. Matter 36 363501
Figure Caption: A microwave photon-magnon chip operating at cryogenic temperatures. (Zhang lab at UNC)
A new review article by Tyndall et al is featured on the cover of the Journal of American Dental Association.
The article describes “Four emerging technologies with promise”, 2 out of those 4 come from Otto Zhou’s lab: intraoral tomosynthesis and multisource CBCT.
The paper “Two-Pole Nature of the Λ(1405) Resonance from Lattice QCD” published by the Baryon Scattering (BaSc) collaboration was recently accepted as editors’ suggestion in the Physical Review Letters. The accompanying paper “Lattice QCD study of πΣ−KN scattering and the Λ(1405) resonance” was also accepted as editors’ suggestion in the Physical Review D.
The role of the fundamental theory of the strong nuclear force, Quantum Chromodynamics (QCD), in the formation of the observed hadron spectrum is an outstanding issue for the standard model of particle physics. The use of QCD to describe the binding of quarks and gluons into hadrons, such as protons and neutrons, is a low-energy phenomenon that requires a nonperturbative calculation that is difficult to apply. The nonperturbative technique we utilize is lattice QCD, where the theory is formulated on a spacetime lattice that allows statistical calculations on computers through Monte Carlo methods. States observed in experiments can be explained using scattering formalism, with theoretical methods necessary to compare calculations on Euclidean spacetime lattices to continuous Minkowski amplitudes. However, the study of nuclear systems using LQCD has been hampered because of a signal-to-noise problem that is heightened when extracting correlation functions. Recent advances in stochastic algorithms have allowed multi-hadron computations and the determination of meson-baryon scattering amplitudes, allowing studies of resonances and excited states in the hadron spectrum.
The work of the BaSc collaboration is the first lattice QCD study of a coupled-channel scattering system containing meson-baryon scattering amplitudes. This work is concerned with explaining the Lambda (1405) resonance which is a spin-1/2, negative parity state first identified experimentally in 1959. Explaining the nature of the Lambda (1405) has been a challenge to nuclear theorists as its relatively low mass and quantum numbers are difficult to explain in the three-quark model of low-energy QCD, leading to exotic explanations of the particle such as the meson-baryon molecular structure. The lattice study in this work utilizes quarks that are slightly heavier than physical and can identify two poles in the complex scattering amplitude with the resonance near the kaon-nucleon threshold and a virtual bound state as the lower pole below the pion-sigma threshold. These results provide a model-independent determination of the scattering amplitude and support the two-pole picture with qualitative results predicted by chiral symmetry and unitarity. This work also opens the use of lattice QCD toward other baryon resonances that can explain the nature of some of the shortest-lived particles observed in experimental physics.
From 2015 until 2021, the Majorana Demonstrator, tucked nearly a mile underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, searched for an elusive decay that might be the key to solving one of the universe’s biggest puzzles: why matter abounds rather than nothingness. The postulated decay, known as neutrinoless double beta decay, if observed would reveal the quantum nature of neutrinos and prove that neutrinos are their own antiparticles.
The experiment’s final results, while not observing the decay, set a limit on the half-life of the decay of greater than 8 x 1025 years (a timescale more than 1015 times longer than the age of the universe). The experiment has helped pave the way for a next generation experiment known as LEGEND that aims to eventually have a hundred times the sensitivity of the Demonstrator.
UNC Physics and Astronomy faculty Julieta Gruszko, Reyco Henning, and John Wilkerson together with Matthew Busch from Duke, faculty member Matthew Green from NCSU, and UNC and NCSU graduate students and postdoctoral scholars made essential contributions to the Majorana efforts. UNC Postdoctoral fellow Ian Guinn (now at Oak Ridge National Laboratory) served as the paper’s corresponding author. This collaborative research was supported and facilitated by the Triangle Universities Nuclear Laboratory(TUNL), a DOE Center of Excellence that is a consortium of UNC, Duke, NCSU, and NCCU nuclear physics researchers.
The Demonstrator was enabled by support from the U.S. Department of Energy Office of Nuclear Physics and the National Science Foundation.
(Left: the Cover of the Article; Right: The Article has the most downloads under the Nuclear Physics section in 2023)
A technological advance in medical and dental imaging promises to improve diagnostic accuracy while minimizing patient exposure to radiation, according to a research article in the Nature journal Communications Engineering.
In the article, “Volumetric Computed Tomography with Carbon Nanotube X-Ray Source Array for Improved Image Quality and Accuracy,” Shuang Xu, a Materials Science Ph.D. candidate in the Department of Applied Physical Sciences, demonstrated that multisource cone beam computed tomography (ms-CBCT), a type of X-ray imaging, has the potential to offer clinicians detailed 3-D imaging that will improve patient care and treatment.
Xu collaborated on the research with UNC-Chapel Hill Professors Christina Inscoe, Jianping Lu and Otto Zhou of the Department of Physics and Astronomy, Don Tyndall of the Adams School of Dentistry and Yueh Lee of the School of Medicine.
The researchers argue that ms-CBCT would be an improvement over conventional CBCT. Conventional CBCT is a specialized medical imaging technique that provides detailed 3-D volumetric images that offer a 360-degree spherical viewing angle of an object. CBCT imaging is used primarily in the fields of dentistry, maxillofacial surgery, interventional radiology and image-guided radiation therapy, where precise visualization of hard-tissue structures like teeth, jaws and the skull is crucial.
“Despite its advantages, conventional CBCT has limitations due to its large imaging volume,” said Xu. “These limitations include reduced soft tissue contrast, image distortion, use that is restricted primarily to imaging hard tissues and hindered quantitative analysis.”
Ms-CBCT overcomes these challenges by enhancing the accuracy of CT imaging of radiodensity of tissues by 60% and soft-tissue contrast by approximately 50%, allowing radiologists and clinicians to distinguish between different tissues and structures within the body. For example, in a CT scan of the abdomen, the liver might have a different HU value than the spleen, helping to identify and characterize abnormalities.
“This is a critical improvement,” said Otto Zhou, David Godschalk Distinguished Professor in the Department of Physics and Astronomy and a member of the APS adjunct faculty, “because accurate HU values are essential for quantitative analysis, tissue characterization and accurate diagnosis.”
In addition to improving image quality and diagnostic accuracy, ms-CBCT reduces the amount of “artifacts,” which can include the presence of metal objects, such as dental fillings or implants, and image distortion due to cone-beam imaging geometry.
“It’s a more comprehensive examination of the imaged area that can be particularly beneficial for capturing larger anatomical structures or regions of interest and improving soft-tissue contrast, making it possible to image more than just hard tissues,” said Xu.
CBCT systems utilize a cone-shaped X-ray beam, as opposed to the fan-shaped beam used in traditional systems. The cone-shaped beam is directed toward the patient or the specific region of interest and a flat-panel detector is positioned opposite the X-ray source. The detector captures the X-rays that pass through the patient, converting them into electrical signals. As the system rotates around the patient, it continuously emits the cone-shaped X-ray beam.
Ms-CBCT involves using multiple X-ray sources configured as an array. Instead of a single, wide cone-angle X-ray tube, this technology employs several X-ray sources that can be strategically positioned around the patient or imaging target. Carbon nanotubes have unique properties that make them suitable for X-ray emission, including their ability to efficiently generate electrons, as well as their small size.
“The ms-CBCT design holds promise for significantly enhancing the capabilities of CBCT scanners,” said Zhou. “These improvements could make CBCT a more versatile tool in medical and dental imaging, potentially competing with multidetector CT images in certain diagnostic applications while retaining its inherent advantages.”