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April 26, 2023: The Future of Nuclear Deterrence and Arms Control

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Category: Department News
Published: Saturday, April 01 2023 01:40

 

“The most significant event of the past 60 years is the one that did not happen: the use of a nuclear weapon in conflict.”

Thomas Schelling (1921-2016), Nobel laureate and UMD Distinguished University Professor, in 2006.Click to read Maryland Today's coverage.Click to read Maryland Today's coverage.

After the fall of the Union of Soviet Socialist Republics (USSR) in 1991, the Doomsday Clock of the Bulletin of the Atomic Scientists—which gauges the likelihood of nuclear war—stood at 17 minutes to midnight. Today, that interval is down to 90 seconds, amid hostilities involving heavily-armed countries, the quest of smaller nations to build nuclear weapons, ongoing economic rivalries and increasing nationalism.   

The avoidance of nuclear conflict since the unspeakable destruction of Hiroshima and Nagasaki in 1945 has required diligent work by the arms control and nuclear deterrence experts of the world's superpowers.

On Wednesday, April 26, at 4 p.m. in Room 0224 of the Edward St. John building, four physicists who are renowned experts on deterrence and arms control will discuss the current global situation.  

  • Roald Sagdeev, former heard of the USSR space agency IKI and advisor to USSR leader Mikhail Gorbachev. Prof. Sagdeev, a pioneer in plasma physics and controlled nuclear fusion, is the recipient of the American Astronautical Society's Carl Sagan Memorial Award and the American Physical Society's James Clerk Maxwell Prize.  He is UMD Distinguished University Professor Emeritus and member of the National Academy of Sciences.

  • John Holdren, former Director of  the White House Office of Science and Technology Policy (OSTP) and Senior Advisor to President Barack Obama on science and technology from 2009-17.  Prof. Holdren is now a Research Professor in Harvard University’s Kennedy School of Government and Co-Director of the Science, Technology, and Public Policy Program in the School’s Belfer Center for Science and International Affairs.

  • Frank von Hippel, former Assistant Director for National Security in the OSTP from 1993-95. Prof. Von Hippel is now a Senior Research Physicist and Professor of Public and International Affairs Emeritus with Princeton’s Program on Science & Global Security, which he co-founded.  

  • Richard Garwin, IBM Fellow Emeritus at the Thomas J. Watson Research Center. Garwin was a member of the President’s Science Advisory Committee from 1962-1965 and 1969-1972, and a member of JASON Defense Advisory Group since its inception. He is a member of the National Academy of Sciences, the National Academy of Medicine, and the National Academy of Engineering, and is a recipient of the Presidential Medal of Freedom.

Moderating the panel will be Susan Eisenhower, author and expert on international security and arms control.  William E. “Brit” Kirwan, chancellor emeritus of the University System of Maryland, will open the forum.

All are welcome to attend, ask questions, and engage the panel. Questions sent in advance to This email address is being protected from spambots. You need JavaScript enabled to view it. will have first consideration. 

Roald Sagdeev Roald SagdeevJohn HoldrenJohn HoldrenFrank von HippelFrank von HippelRichard GarwinRichard GarwinSusan EisenhowerSusan Eisenhower

 

Writeup of the event by the University of Maryland School of Public Policy: https://spp.umd.edu/news/eminent-nuclear-physicists-convene-umd-discuss-future-nuclear-deterrence-and-arms-control

Manuel Franco Sevilla Receives Junior Faculty Award

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Category: Department News
Published: Tuesday, February 21 2023 05:07
Manuel Franco Sevilla installs ODMB modules into the CMS detector at CERN. (Photo: Jeff Richman)

Manuel Franco Sevilla has received the 2022 Junior Faculty Award from the Board of Visitors of the College of Computer, Mathematics and Natural Sciences in recognition of his “exceptional accomplishments that have raised the profile and prestige of the college”.

Franco Sevilla is a particle physicist doing research at CERN’s Large Hadron Collider’s beauty (LHCb) experiment, which employs “beauty” (or “b”) hadrons produced in high-energy collisions of protons to study the fundamental laws of our Universe.Manuel Franco Sevilla Manuel Franco Sevilla

His research focuses on measurements that test lepton universality, a fundamental assumption within the Standard Model of particle physics that states that the interactions of all charged leptons (electrons, muons, and taus) differ only because of their different masses. His thesis in 2012 saw the first hints of possible lepton universality violation, and since then, several measurements in experiments across the world have found similar hints. He has covered this topic in multiple international forums and in reviews for Nature and Review of Modern Physics.

Additionally, Franco Sevilla works on the Upstream Tracker (UT), a new silicon tracker that is a crucial part of LHCb’s ongoing upgrade to achieve data taking rates five times larger than previously possible. Together with Professor Hassan Jawahery, he co-led the development and production of the readout electronics for the UT, a total of over 600 main boards and 3,000 ancillary ones. This immense effort included contributions from an electronics engineer, three postdocs, four graduate students and the recruitment and training of a group of 12 undergraduate students who were instrumental during the testing and assembly phases of the project.

Last year Franco Sevilla was named deputy project leader of the UT and spent the second half of 2022 at CERN coordinating the assembly and installation of this subdetector into the LHCb experiment, an effort that involved a team of over 25 engineers, technicians, postdocs, and students as well as other CERN resources such as survey, transportation, or radiation protection teams. Some pictures of theses activities are shown below.

(Possibly) Breaking the Standard Model, One Lepton-universality-violating Decay at a Time

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Category: Research News
Published: Thursday, February 09 2023 02:53

Physicists in general, and high energy physicists in particular, like to "break" things. It can be useful to prove again that a well established theory is true, especially if you are probing a yet-untested prediction of the venerable theory. But proving that the theory is wrong--or at least not completely true--that is where the fun is. This is why a series of measurements of b hadron decays that seemingly break the Standard Model (SM) of particle physics is garnering so much excitement.

You see, the SM is the most well established theory of them all, the only one with predictions corroborated to the 11th digit (see the anomalous magnetic moment of the electron). It was fully fleshed out in the 70's, and since then it has racked up success after success. Its crowning achievement came in 2012 when the long-predicted Higgs boson was finally confirmed to be alive and well. Despite this resiliency, the SM is not the end of it all. It can't explain why the mass of the Higgs is so low, what the nature of dark matter is, or why there is so much more matter than antimatter in the universe. Finding answers to these questions will thus require breaking, or extending, the SM.

Enter Lepton Flavor Universality (LFU) violation. LFU is a fundamental assumption within the SM involving the three lepton flavors: electron, muon, and tau. All SM interactions other than the Higgs are assumed to be flavor universal, and this has been shown to be true in numerous measurements. Since 2012, however, an intriguing pattern has emerged in decays of b hadrons (particles with a b quark inside) to final states with a c quark, a tau lepton τ, and a neutrino ν. When results involving a tau lepton and a neutrino are compared to decays involving a muon or an electron and a neutrino, they tend to be higher than we'd expect from SM calculations. This is shown in the nearby figure by all the measurements keeping their distance from the theoretical predictions in blue. Measurements that measured the two LFU quantities RD and RD* are shown as Artistic representation of a proton-proton collision resulting in a B meson that subsequently decays to a charmed D0 or D* meson, a tau lepton, as well as a smaller antineutrino. Credit: Greg Stewart, SLAC National Accelerator Laboratory/BaBar and Manuel Franco Sevilla.Artistic representation of a proton-proton collision resulting in a B meson that subsequently decays to a charmed D0 or D* meson, a tau lepton, as well as a smaller antineutrino. Credit: Greg Stewart, SLAC National Accelerator Laboratory/BaBar and Manuel Franco Sevilla.ellipses while measurements of RD* alone are shown as markers with uncertainties.
 
None of these results on their own rises to what is typically known as an "observation" (5σ statistical significance), and it could very well go away. For instance, a similar pattern that had appeared when comparing decays involving a kaon and two muons to decays with a pair of electrons was recently shown to be an artifact  of an underestimated background. But the consistency among results that share the same b→ cτν underlying process is very suggestive. Multiple explanations have been proposed that would explain all of these with physics beyond the SM (BSM). A particularly neat solution postulates a new kind of exotic particle that interacts with both leptons and quarks: a vector leptoquark. 
 
In an article published last year in Review of Modern Physics ("Semitauonic b-hadron decays: A lepton flavor universality laboratory"), my co-authors and I comprehensively described these results, delved into the main sources of uncertainty, and mapped out the future measurements. Spoiler alert: while we do not know whether BSM physics will be discovered, we are rather confident that we will know whether these results are due to BSM physics or not within 5-10 years. 
 
And the first of these new results was just submitted to Physical Review Letters  Professor Hassan Jawahery and Dr. Phoebe Hamilton, together with Dr. Greg Ciezarek from CERN, measured for the first time RD and RD* simultaneously at LHCb. The uncertainties are still large, so it is hard to say whether the discrepancy will be proven true. But this result sets the stage for another meaThe results reflect analysis of two years of data by Phoebe Hamilton and Hassan Jawahery and their CERN collaborator, Greg Ciezarek.The results reflect analysis of two years of data by Phoebe Hamilton and Hassan Jawahery and their CERN collaborator, Greg Ciezarek.surement based on the same techniques that uses a data sample more than 6 times larger. This work, carried out by the all-UMD team Professor Manuel Franco Sevilla, Dr. Hamilton, Dr. Christos Hadjivasiliou, Yipeng Sun, and Alex Fernez, is now fairly advanced. So stay tuned, there's potential for SM-breaking ahead!
 
 
 
 

 --Manuel Franco Sevilla

 

  

James J. Griffin, 1930-2022

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Category: Department News
Published: Sunday, February 05 2023 10:37

Professor Emeritus James J. Griffin died on December 13, 2022.

Griffin earned his Ph.D. in theoretical physics at Princeton University in 1956 and then accepted a Fulbright Scholarship to the Institute for Theoretical Physics in Copenhagen. Following a National Science Foundation Fellowship at the University of Birmingham and an appointment as a Visiting Lecturer at the University of Wisconsin, he joined UMD as an assistant professor in 1966. He was promoted to associate professor and full professor in 1968 and 1973, respectively. In the 1968-69 academic year, Griffin served as Associate Chair of the UMD Department of Physics and Astronomy.

Griffin studied nuclear structure and heavy ions, and was perhaps best known for his publication, “The statistical model of intermediate structure,” which appeared in Physical Review Letters.  He received a John Simon Guggenheim Foundation Fellowship to work at the Lawrence Berkeley Laboratory in 1972-73. In 1975, he received an Alexander von Humboldt Foundation Senior Scientist Fellowship and worked at the Justus Liebig University in Giessen and the Hahn Meitner Institute for Nuclear Research in Berlin.   

During his career, Griffin also enjoyed visiting positions at Los Alamos National Laboratory, Oak Ridge National Laboratory, the University of California in Berkeley, and several institutions in France and Germany. He was an invited guest lecturer in Germany, Canada, Poland, China, Israel, Japan, France and Romania. 

A memorial is planned for the spring. If you'd like to be notified when it is scheduled, please contact This email address is being protected from spambots. You need JavaScript enabled to view it..

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