Research, teaching and outreach in Physics at UW–Madison
Alex Wang selected for DOE’s Office of Science Graduate Student Research program
Congratulations to physics graduate student Alex Wang, who is one of 65 graduate students selected for the Department of Energy’s Office of Science Graduate Student Research (SCGSR) program. He is a student in Prof. Sau Lan Wu’s group.
SCGSR awardees work on research projects of significant importance to the Office of Science mission and that address societal challenges at national and international scale. Wang’s research is part of the priority research area of High Energy Physics. Awardees carry out part of their research at a DOE national lab, and his host lab is the SLAC National Accelerator Laboratory.
“The DOE Office of Science provides the scientific foundation for solutions to some of our nation’s most complex challenges, and now more than ever we need to invest in a diverse, talented pipeline of scientists, engineers, and entrepreneurs who can help us build a brighter future,” said Dr. Harriet Kung, Deputy Director for Science Programs in the Office of Science. “These outstanding students will help us tackle mission-critical research at our labs as this experience helps them begin a successful and rewarding career.”
Awardees were selected from a diverse pool of graduate applicants from institutions around the country. Selection was based on merit peer review by external scientific experts.
Sau Lan Wu featured in AIP History newsletter
A biography of Professor Sau Lan Wu was included as the cover story in a recent issue of the AIP History Newsletter (see pages 14-15). The story covers her early life in Hong Kong, her arrival in the U.S. to attend college at Vassar which she attended on a full scholarship, and into her graduate studies and subsequent research programs at MIT, UW–Madison and CERN. There is also a list of references / further readings. Check out the article to learn more about Prof. Wu’s illustrious career so far!
Yang Bai promoted to full professor
The Department of Physics is pleased to announce that Prof. Yang Bai has been promoted to the rank of full professor.
“It is my pleasure and honor as Dean to approve Prof. Yang Bai’s promotion to Full Professor. His creativity and impressive breadth in particle physics research make him a leader not only on dark matter, but also more generally on Beyond-the-Standard-Model Physics,” says Eric Wilcots, Dean of the College of Letters & Science. “He is also a valued teacher, appreciated by students especially at the graduate level. Graduate students and junior researchers in Madison are in good hands.”
Bai joined the department in 2012, and was promoted to associate professor in 2017. In addition to his robust and well-funded research program, he has trained several successful graduate students, taught all levels of departmental courses, and served on several departmental and university committees.
“Professor Yang Bai is widely recognized as one of the leading theoretical particle physicists of his generation with a broad and vigorous research program, covering both the collider-related frontiers and the cosmic frontier. His work includes significant contributions in essentially every area related to dark matter,” says Sridhara Dasu, professor and department chair. “The Physics Department very strongly endorses the promotion of Yang Bai to Full Professor.”
Congrats, Prof. Bai on this well-earned recognition!
CMS Group publishes new study on Lepton flavor in Higgs boson decays
Neutrinos mix and transform from one flavor to the other. So do quarks. However, electron and its heavier cousins, the muon and the tau, seem to conserve their flavor identity. This accidental conservation of charged lepton flavor must have a profound reason, or low-levels of violation of that conservation principle should occur at high energy scales. However, evidence for any charged lepton flavor violation remains elusive.
The international CMS collaboration recently published a news story about this new study. Please read the full story here.
Highest-energy Cosmic Rays Detected in Star Clusters
For decades, researchers assumed the cosmic rays that regularly bombard Earth from the far reaches of the galaxy are born when stars go supernova — when they grow too massive to support the fusion occurring at their cores and explode.
Those gigantic explosions do indeed propel atomic particles at the speed of light great distances. However, new research suggests even supernovae — capable of devouring entire solar systems — are not strong enough to imbue particles with the sustained energies needed to reach petaelectronvolts (PeVs), the amount of kinetic energy attained by very high-energy cosmic rays.
And yet cosmic rays have been observed striking Earth’s atmosphere at exactly those velocities, their passage marked, for example, by the detection tanks at the High-Altitude Water Cherenkov (HAWC) observatory near Puebla, Mexico. Instead of supernovae, the researchers — including UW–Madison’s Ke Fang — posit that star clusters like the Cygnus Cocoon serve as PeVatrons — PeV accelerators — capable of moving particles across the galaxy at such high energy rates.
New UW–Madison assistant professor of physics Lu Lu’s research program combines the past with the future. Her research looks for sources of ultrahigh energy particles, which is done by analyzing data that has already been collected. As she says, “Maybe data is already talking to us, we just haven’t looked.” But she is also working toward improving future data collection, which will require more technologically-advanced detectors. “My teachers, my great masters, have taught me that the current young generation has the responsibility to look into new techniques to go to the future for younger generations to proceed forward,” she says about her work in sensor R&D.
On January 1, Professor Lu joined the Department of Physics and IceCube. Most recently, she was a postdoctoral fellow at the International Center for Hadron Astrophysics at Chiba University in Japan. To welcome her, we sat down for a (virtual) interview.
What are your research interests?
My prime interest is astroparticle physics, and my ultimate goal is to find the sources of the highest energy particles in the universe. These particles carry energy of about 1020 electronvolts. This is higher energy than what we have from the Large Hadron Collider and human technologies. The real attractiveness here is we don’t know how nature accelerates these particles. And once we identify the sources, we can test new theories beyond the Standard Model using sources crated by nature.
What are one or two main projects you focus your research on?
I’m involved in two experiments. One is IceCube, the other is Pierre Auger Observatory. I was doing cosmic ray analysis, but cosmic rays are usually charged particles and they are deflected in the magnetic field of the galaxy; they would not travel in a straight line. IceCube studies neutrinos which are neutral particles, they travel directly from the source. Pierre Auger detects ultrahigh energy photons, which are also neutral particles. One thing I want to do immediately after I join Madison is to combine these two experiments to do a joint analysis. We have photon candidates but we haven’t really tried to connect them in the multimessenger regime. By combining Pierre Auger photons with IceCube neutrinos, we could possibly find a transient source, a source that doesn’t constantly emit ultrahigh energy photons or neutrinos but all of a sudden there’s a flare. This type of analysis has never been done, but we have data on disks.
The second thing I’m interested in is using new sensor technologies. In IceCube, we have Gen2 being planned right now. Instead of using a single photon sensor, we’d use a more sensitive design and R&D. UW–Madison is taking the lead of designing this future detector. There’s also radio technology. So, to detect the highest energy neutrinos we need to build a large instrument volume. With optical array, it is really hard to scale up because one has to drill holes inside the South Pole, which is really expensive. But radio technology doesn’t have to go so deep, so they can bury their detectors on the surface areas, and the radiowaves can transmit further away than the optical photons in ice. For optical you have to make the detectors very dense, but for radio you can make the antennas further apart, so that means you can have a larger area and detect more events easily. I think radio is the way to go for the future.
You said you have a lot of data collected already and just need to analyze it. How do you analyze the data from these detectors?
We would have to search for photon candidates from the data from Auger, and identify where it comes from and what the time this event happened. Correspondingly, do we see neutrinos from IceCube coming from the same direction and at the same time? Because you can never be sure it’s a photon. It could be a proton. We then want to build a statistical framework to combine different multimessengers together in real time.
What does it mean if you find a photon in coincidence with a neutrino?
Cosmic rays were first detected more than 100 years ago, and there’s a rich history of studying where they come from. The mystery of origins still remains today because our poor knowledge on the galactic/extragalactic magnetic fields and mass composition of cosmic rays. In my opinion, the most probable way to solve this puzzle is to use neutral particles. If we can identify ultrahigh energy photons in coincidence with neutrinos, that is a smoking gun that we are actually looking at a source and we can finally pin down where in the universe is accelerating high energy particles. And therefore, we can study particle physics maybe beyond Standard Model. It’s just like a lab created by the universe to test particle physics.
What is your favorite element and/or elementary particle?
My favorite elementary particle is the electron anti-neutrino. I like muons, too. My favorite element is hydrogen.
What hobbies and interests do you have?
I’m afraid I’ll disappoint you because my hobby is related to my research: Augmented reality. When I heard about something called Microsoft Hololens, I thought, I could make IceCube a hologram. I bought these special glasses, and then made a program on it and used it for some outreach events. But the glasses are very expensive, so people said, “Okay we can’t buy hologram glasses.” So I moved it to mobile phones so that everyone could look at it for fun. It’s called IceCubeAR (note: download it for iPhones or Android phones). I made it with a group of friends in Tokyo.
Scientists Say Farewell to Daya Bay Site
The Daya Bay Reactor Neutrino Experiment collaboration – which made a precise measurement of an important neutrino property eight years ago, setting the stage for a new round of experiments and discoveries about these hard-to-study particles – has finished taking data. Though the experiment is formally shutting down, the collaboration will continue to analyze its complete dataset to improve upon the precision of findings based on earlier measurements.
The detectors for the Daya Bay experiment were built at UW–Madison by the Physical Sciences Laboratory, and detailed in a 2012 news release.
Says PSL’s Jeff Cherwinka, U.S. chief project engineer for Daya Bay:
The University of Wisconsin Physics Department and the Physical Sciences Lab were very involved in the design, fabrication and installation of the anti-neutrino detectors for the Daya Bay Experiment. It was a great opportunity for faculty, staff, and students to participate in an important scientific measurement, while learning about another country and culture. There were many trips and man years of effort in China by UW physicists, engineers and technicians to construct the experiment and many more for operations and data taking. This international collaboration took a lot of effort, and in the end produced great results.
The chief experimentalist at UW–Madison was Karsten Heeger who has since left for Yale. At present, Prof. Baha Balantekin is the only one remaining at UW–Madison in the Daya Bay Collaboration.
Researchers awarded Department of Energy Quantum Information Science Grant
Three UW–Madison physics professors and their colleagues have been awarded a U.S. Department of Energy (DOE) High Energy Physics Quantum Information Science award for an interdisciplinary collaboration between theoretical and experimental physicists and experts on quantum algorithms.
The grant, entitled “Detection of dark matter and neutrinos enhanced through quantum information,” will bring a total of $2.3 million directly to UW-Madison. Physics faculty include principal investigator Baha Balantekin as well as Mark Saffman, and Sue Coppersmith. Collaborators on the grant include Kim Palladino at the University of Oxford, Peter Love at Tufts University, and Calvin Johnson at San Diego State University.
With the funding, the researchers plan to use a quantum simulator to calculate the detector response to dark matter particles and neutrinos. The simulator to be used is an array of 121 neutral atom qubits currently being developed by Saffman’s group. Much of the research plan is to understand and mitigate the behavior of the neutral atom array so that high accuracy and precision calculations can be performed. The primary goal of this project is to apply lessons from the quantum information theory in high energy physics, while a secondary goal is to contribute to the development of quantum information theory itself.
High Energy Physics group awarded three grants totaling over $14 million
The High Energy Physics (HEP) group at UW–Madison, which broadly focuses on identifying and understanding the fundamental aspects of particles and forces in Nature, has been awarded three significant grants in 2020. The grants — two from the Department of Energy (DOE) and one from the National Science Foundation (NSF) — are awarded either directly to UW–Madison or indirectly through multi-institution international collaborations, bringing over $14 million to the department.
The first grant, $7.37 million from DOE, funds research that is expected to help physicists understand how our Universe works at its most fundamental level. At UW–Madison, this research includes experimental and theoretical studies into topics such as using the Higgs boson as a tool for new discoveries and identifying principles of dark matter.
The grant will fund five areas of research: 1) studies of high energy proton-proton collisions; 2) studies of neutrino interactions; 3) studies of super-weak signals from galactic dark matter particles; 4) wide-area imaging surveys using powerful new telescopes; and 5) computational and mathematical methods of quantum field theory and string theory.
The other two grants awarded will provide funding for upgrades to the Compact Muon Solenoid (CMS) project at the Large Hadron Collider (LHC) at CERN. The first is an NSF-funded grant for which Kevin Black is leading the UW–Madison effort to upgrade the CMS End Cap muon system upgrade. The $900,000 to the department is part of a larger multi-institutional grant through Cornell University and runs through 2025.
“The GEM detectors are novel micropattern gas detectors which can handle the high background rates expected in the end-cap muon detectors. They will enhance the triggering and reconstruction of forward muons which are expected to make significant improvements and increased acceptance to search for new particles and make precision measurements of known particles and interactions,” Black explains. “UW has a long history with CMS muon system with Prof Matt Herndon, Senior Emeritus Scientist Dick Loveless, and Senior Scientist Armando Lanaro leading to the design, construction, operation, and upgrade of the other end-cap subdetector system instrumented with Cathode Strip Chambers.”
The other CMS-specific grant is a four-year, $5.3 million DOE grant through Fermilab that will fund the CMS trigger upgrade. This funding will allow the UW–Madison CMS group to perform all aspects of the work involved in design, prototyping, qualification, production and validation of the calorimeter trigger system for the upgrade. When completed, the project is expected to result in the collection of 25 times more data than is currently possible. Sridhara Dasu is the principal investigator of this grant.
The J.J. Sakurai Prize is considered one of the most prestigious annual prizes in the field of theoretical high energy physics. Barger, who joined the UW–Madison faculty in 1965, is a world leader in theoretical particle physics where theory meets experiment. He is one of the founders of collider phenomenology as it is practiced today.
“This prize belongs to the hundreds of students, postdocs, faculty and visiting colleagues who entered the portal of UW–Madison to discover the quarks, leptons and bosons of particle physics,” Barger says. “Only at UW–Madison could this research at the interface of theory and experiment so thrive.”
The techniques that Barger helped develop have been crucial in establishing the experimental foundations of the Standard Model of particle physics and in guiding the search for signals of new physics. His contributions have played a key role in many important milestones in particle physics, including the discovery of the W boson in 1985, the top quark in 1995, and the Higgs boson discovery in 2012.
UW–Madison physics professor Lisa Everett and University of Hawaii professor Xerxes Tata, both phenomenologists, co-nominated Barger for the prize.
“We are thrilled that Vernon Barger has been awarded the 2021 J.J. Sakurai Prize, for which we nominated him for his seminal accomplishments and leadership record in collider physics phenomenology over five decades in the field,” Everett says. “The techniques he has pioneered have and continue to be of pivotal importance for elucidating physics signals at particle colliders, and these contributions are only part of a very long and distinguished research career in theoretical particle physics. He is highly deserving of this honor.”