Faculty

Welcome, Professor Ke Fang!

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By Madeleine O’Keefe, WIPAC

When you think of scientific meccas throughout the world, Madison, Wisconsin might not be the first place that comes to mind. But for astroparticle physicist Ke Fang, Madison is the place to be. That’s because it’s home to the Wisconsin IceCube Particle Astrophysics Center (WIPAC): the “leader of particle astrophysics in the world,” according to Fang. “Throughout the years, there have been all kinds of meetings and workshops that drive people in this field to Madison because it’s the center for particle astrophysics,” she says.

Ke Fang

Originally from Huangshan, China, Fang earned a B.S. in physics from the University of Science and Technology of China. Afterward, Fang moved to the United States for graduate school and earned her PhD in astrophysics from the University of Chicago in 2015. Following that, she went to the University of Maryland and the Goddard Space Flight Center for a Joint Space-Science Institute fellowship. Most recently, Fang was a NASA Einstein Fellow at Stanford University in California.

Now, Fang has joined WIPAC and the UW–Madison Physics Department as an assistant professor. To welcome Fang and learn more about her, we met up on—where else?—Zoom for an interview.

 Can you summarize your research? 

I use both experiments and theory to understand extreme activities of our universe. We receive multiple types of messengers from the universe—all the way from optical light to gamma rays, cosmic rays, neutrinos, and gravitational waves. These messengers can be emitted by a common source, such as a binary neutron star merger. Specifically, I use theoretical models to understand how these astrophysical events produce different messengers, whether theoretical models explain the data, and how the data compare with theoretical models. I also use the HAWC Observatory, the IceCube Neutrino Observatory, and the Fermi Large Area Telescope (Fermi-LAT) to observe or to find sources directly. For example, I jointly analyze the Fermi-LAT and HAWC data to observe gamma-ray sources from 0.1 GeV to 100 TeV—across six orders of magnitude. Studies using multiple messengers and wavelengths are rewarding because they help us get a full picture of what these astrophysical sources look like.

How did you get into your field of research?

When I started graduate school, high-energy astrophysics was rather new; it’s a field that has quickly grown in the past decade or so. High-energy astrophysics traditionally refers to astrophysics with X-ray observations, because X-rays are higher in energy compared to the optical band that astronomers traditionally use. But in the last few years, high-energy astrophysics has had another burst of delving into even higher energies. When we move up in energy, by millions or billions, we see many new sources that were previously not observable in the X-ray band, or different aspects of sources that were previously seen at lower energies. And there are so many unknowns in this field; we can see surprising things at the highest energies, and many of those observations are discoveries. I think that’s really intriguing.

 What attracted you to UW–Madison and WIPAC? 

I think it’s pretty fair to say that WIPAC—with IceCube, CTA, HAWC, Fermi-LAT, ARA, and IceCube-Gen2—is now the leader of particle astrophysics in the world. I think there’s a close match between my expertise and what is currently being done at WIPAC, and I’m excited about joining the department and joining these explorations of higher and higher energy neutrinos and gamma rays.

What’s one thing you hope students who take a class with you will come away with?

The content you learn from a class is limited, but the contexts where you could apply the knowledge are unlimited.

 What is your favorite particle?

Neutrino. If I have to pick one, neutrino is the one that I have in my heart.

What hobbies/other interests do you have?

 Cooking! I like to explore different things. I come from China, so Chinese cuisine is what I started from when I just moved to the United States. But after all these years, I’m getting more exposed to different types of cuisines and starting to explore more, like with Thai and Italian. When I go to nice restaurants, I try to remember the name of the dish and find the recipe online.

 

 

Welcome, Professor Lu Lu!

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Lu Lu

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

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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.

A completion ceremony will be held Friday, December 11from 7:30-8:3opm CST. Video stream options and the full story can be found at Berkeley Lab’s website.

Pupa Gilbert elected Fellow of the Mineralogical Society of America

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Proflie photo of Pupa Gilbert

Congrats to Prof. Pupa Gilbert on her election as a Fellow of the Mineralogical Society of America! Members who have contributed significantly to the advancement of mineralogy, crystallography, geochemistry, petrology, or allied sciences and whose scientific contribution utilized mineralogical studies or data, may be designated as Fellows upon proper accreditation by the Committee on Nomination for Fellows and election by the Council. The number of fellows elected each year cannot exceed 0.5% of MSA membership.

Fellows newly elected in 2020 are Jeffrey Catalano, Sylvie Demouchy, Pupa Gilbert, Jun-ichi Kimura, Othmar Muntener, Marc Norman, Alison Pawley, Mark Rivers, Ian Swainson, and Takashi Yoshino.

Full list of MSA Fellows

Welcome, Professor Uwe Bergmann!

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Uwe Bergmann

From bird feathers that allow for perfectly efficient flight to the bacterial enzyme that fixes nitrogen to help plants grow, nature has had a lot of time to figure things out. “There are so many things we need to be learning how to do from nature, because our methods are still much inferior to those!” says UW–Madison’s newest physics professor, Uwe Bergmann, the Martin L. Perl Professor in Ultrafast X-ray Science. “I think we are going in this direction of learning more and more from nature and using this knowledge to run our world sustainably, but still in a modern way. And that theme brings physicists and many other domains together.”

Bergmann is a physicist who develops and applies x-ray techniques to chemical, biological, engineering, and even archaeological research questions, trying to understand at the atomic level what nature has perfected over a few billion years. Prior to joining the Department on December 1, Bergmann was a Scientist at SLAC. Here, he will focus his research program on continuing to develop and apply novel x-ray techniques. To welcome Bergmann, we sat down for a (virtual) interview.

What is an overview of your research?

My research is developing and applying x-ray methods to solve problems. And these problems can be uncovering hidden writings in ancient books or the chemical elements buried in fossils to reveal the color in the original animal; studying photosynthetic water splitting to understanding the structure of liquid water; and making movies of a molecule carrying out specific work.

What techniques do you use in your research?

I use mainly x-ray techniques, and we do x-ray spectroscopy and sometimes also x-ray scattering and diffraction. The basic difference is that diffraction and scattering looks at the geometric structure — where are the atoms? — and spectroscopy looks at the chemical structure — where are the electrons? Recently we have been using powerful new x-ray lasers, where you can make ultrafast movies showing how chemical bonds are changing in real time. I also use x-ray fluorescence, which is a very powerful imaging technique for creating elemental maps showing the chemical composition of fossils for example.

Once your lab is up and running in Madison, what big projects will you focus on first?

I want to set up a new ultrafast x-UV laser system, able to making these molecular movies with femtosecond resolution. We want to make movies of fast chemical reactions and structural changes; when you expose a material to a light pulse and then watch how the atoms and electrons rearrange after the pulse. This is important for the next generation of advanced materials and a famous example is the water splitting reaction in plants to make O2. We still do not exactly know the mechanism of how these two water molecules are brought in, split up, and forced to make the bond to form O2.

In our latest project with x-ray fluorescence imaging we have scanned more than 50 pages of an ancient parchment book containing the work of the famous Greek physician, Galen of Pergamon. This so-called palimpsest contains a Syriac translation with his work including ‘On Simple Drugs’, which had been erased and overwritten with hymns in the Middle Ages, and catalogued as a new find at Saint Catherine’s Monastery in 1975. Scholars are interested in this translation as it gives information of how Galen’s work originally written in Greek spread east, were it became very popular in the Arab world. Using powerful synchrotron x-rays, we found that you can actually bring out this erased and overwritten text. And scholars can now read it! Key to this success was our new scanning system that records the whole x-ray fluorescence spectrum at each pixel of the image, and our collaborators’ ability to apply advanced machine learning algorithms to enhance the faint traces of overwritten text.

Another exciting project we are working on is an x-ray laser oscillator. There are currently five very big hard x-ray free electron lasers around the world, but they operate in a single pass, which means they are not very stable. Our idea is to use a train of pulses from one of these big x-ray lasers — those are the not-so-clean pulses — to pump our gain medium. After the first pulse creates amplified spontaneous emission, we guide the emitted beam through a cavity made of four mirrors back to the same gain medium to meet up with the next pump pulse from the train. Doing this again and again and again, lets us crank up the beam until we have a perfect, clean and stable x-ray laser pulse, and at the point we will send it out of the cavity. This is similar to how most optical lasers work. We described the idea in PNAS earlier this year, and now we have a lot of work ahead to turn it into reality.

What attracted you to UW–Madison?

For some time, I have been thinking whether it would be possible one day to combine my research activities with teaching at a university. The ultrafast x-ray science chair in the Physics Department was a perfect opportunity and an excellent fit to the research I have been pursuing my entire career. Still, it wasn’t until my visit to Madison, experiencing the wonderful interaction with the students, faculty and staff, and feeling the energy on this beautiful campus, that I fell in love with the idea of joining UW–Madison.

What is your favorite element and/or elementary particle?

Manganese is my favorite element, just because I have been spending so many years studying it and it has so many amazing properties. It’s chemically very important as it has all these different oxidation states, ranging from +2 to +7. And it’s at the heart of the tiny little machine driven by sun light that nature uses to split water into oxygen, which I think is the most important reaction on the planet. Without that reaction there would only be primitive bacterial life on earth. For the elementary particle, I feel almost ashamed but of course it has to be the electron, because it does all the work. Nuclei hardly notice any chemical change, but electrons do all the bonding, all the rearrangements that make the world run; they are the worker bees of nature.

What hobbies/other interests do you have?

I love nature, animals, music, and outdoor activities, especially in and around water.

 

High Energy Physics group awarded three grants totaling over $14 million

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a woman in a helmet wearing a disposable facemask stands in front of lots of metal hardware and wires
HEP post-doc Dr. Camilla Galloni next to the CMS end cap supporting the GEM detectors that were installed this fall. The primary structure in this photo was engineered at the UW–Madison Physical Sciences Lab. The big CSC chambers were installed, upgraded and reinstalled and operated by UW physicists. The smaller GEM chambers, which are barely visible in the interstices, are being commissioned by UW–Madison physicists through the second grant mentioned in this post.

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.

Sridhara Dasu is principal investigator on this DOE grant. Co-investigators include Yang Bai, Vernon Barger, Keith Bechtol, Kevin Black, Tulika Bose, Lisa Everett, Matthew Herndon, Kimberly Palladino, Brian Rebel, Gary Shiu, Jennifer Thomas (WIPAC), and Sau Lan Wu. The grant was awarded in June 2020 and provides funding through March 2023.

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.

Surprising communication between atoms could improve quantum computing

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A dark room with pink-hued lasers reflecting off of mirrors
In their experiments, UW–Madison physicists led by Deniz Yavuz immobilized a group of rubidium atoms by laser-cooling them to just slightly above absolute zero. Then, they shined a laser at rubidium’s excitation wavelength to energize electrons. PHOTO COURTESY OF YAVUZ LAB

A group of University of Wisconsin­–Madison physicists has identified conditions under which relatively distant atoms communicate with each other in ways that had previously only been seen in atoms closer together — a development that could have applications to quantum computing.

The physicists’ findings, published Oct. 14 in the journal Physical Review A, open up new prospects for generating entangled atoms, the term given to atoms that share information at large distances, which are important for quantum communications and the development of quantum computers.

“Building a quantum computer is very tough, so one approach is that you build smaller modules that can talk to each other,” says Deniz Yavuz, a UW–Madison physics professor and senior author of the study. “This effect we’re seeing could be used to increase the communication between these modules.”

profile photo of Deniz Yavuz
Deniz Yavuz

The scenario at hand depends on the interplay between light and the electrons that orbit atoms. An electron that has been hit with a photon of light can be excited to a higher energy state. But electrons loathe excess energy, so they quickly shed it by emitting a photon in a process known as decay. The photons atoms release have less energy than the ones that boosted the electron up — the same phenomenon that causes some chemicals to fluoresce, or some jellyfish to have a green-glowing ring.

“Now, the problem gets very interesting if you have more than one atom,” says Yavuz. “The presence of other atoms modifies the decay of each atom; they talk to each other.”

Read the full  UW–Madison news story

Vernon Barger earns 2021 APS Sakurai Prize

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Vernon Barger

University of Wisconsin­–Madison Physics professor Vernon Barger has won the J.J. Sakurai Prize for Theoretical Particle Physics, the American Physical Society announced October 7.

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.”

UW–Madison chemistry professor Martin Zanni also won an APS award, the Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics. Read the UW–Madison news piece about both Barger and Zanni’s awards here.

Robert McDermott elected Fellow of the American Physical Society

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Robert McDermott

Congratulations to Prof. Robert McDermott, who was elected a 2020 Fellow of the American Physical Society! He was elected for seminal contributions to quantum computing with superconducting qubits, including elucidating the origins of decoherence mechanisms, and development of new qubit control and readout methods. He was nominated by the Division of Quantum Information.

APS Fellowship is a distinct honor signifying recognition by one’s professional peers for outstanding contributions to physics. Each year, no more than one half of one percent of the Society’s membership is recognized by this honor.

See the full list of 2020 honorees at the APS Fellows archive.

Massive halo finally explains stream of gas swirling around the Milky Way

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a starscape showing the milky way in the distance and a rendering of the gases surrounding the large magellenic cloud
The Large and Small Magellanic Clouds as they would appear if the gas around them was visible to the naked eye. | Credits: Scott Lucchini (simulation), Colin Legg (background)

The Large and Small Magellanic Clouds are satellite galaxies of the Milky Way. They are surrounded by a high-velocity gaseous structure called the Magellanic Stream, which consists of gas stripped from both clouds. So far, simulations have been unable to reconcile observations with a complete picture of how the stream was formed. In this Nature week’s issue, numerical simulations carried out at by Scott Lucchini, graduate student at the Physics Department working with Elena D’Onghia, present a model that potentially resolves this conundrum. By embedding the Large Magellanic Cloud in a corona of ionized gas, the researchers were able to simulate the Magellanic Stream accurately and explain its structure. Ellen Zweibel and Chad Bustard are also co-authors of the article.

Read the full UW news story | Read the Nature article