Young-Kee Kim

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ORAL HISTORIES
Young-Kee Kim

Credit: U.S. Department of Energy

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Young-Kee Kim by David Zierler on January 5, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/46825

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Interview with Young-Kee Kim, Louis Block Distinguished Professor of Physics, Chair of the Department of Physics, and Senior Advisor to the Provost for Global Scientific Initiatives at the University of Chicago. She explains her advisory role to the Provost and she surveys the many challenges associated with remote work during the pandemic. Kim recounts her childhood in South Korea, her early interests in math, and her plans in college to pursue a career in theoretical physics. She describes the opportunities that allowed her to come to the United States to pursue thesis research at the University of Rochester to work with Steve Olsen on the AMY experiment and to test QCD via properties of quarks and gluons. Kim describes her postdoctoral work at Berkeley Lab on the CDF experiment at Fermilab, and she explains her decision to join the faculty at UC Berkeley as she was becoming more involved in ATLAS at CERN. She describes the shutdown of the Tevatron and her appointment as Deputy Director of Fermilab, and she explains her decision to move to the University of Chicago. Kim describes the broader view she gained of the DOE in her leadership role at Fermilab and she surveys the reverberating discoveries that occurred as a result of finding the Higgs at the LHC. She explains why electromagnetism is her favorite course to teach and she reflects on the physics community’s recent push to emphasize the importance of diversity and inclusivity. At the end of the interview, Kim conveys the value of taking a global approach to the biggest questions in science and she explains why she remains focused on the Higgs boson, which she believes could offer a pathway to the discovery of new physics. 

Transcript

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is January 5th, 2021. I'm so happy to be here with Professor Young-Kee Kim. Young-Kee, it's great to see you. Thank you so much for joining me today.

Kim:

Thank you.

Zierler:

All right, so to start, would you please tell me your title and institutional affiliation?

Kim:

My title (laughter). Okay. I'm Louis Block Distinguished Service Professor of Physics. I have several titles-

Zierler:

I know.

Kim:

If you don't mind.

Zierler:

Please.

Kim:

I'm also the Chair of the Department of Physics, and Senior Advisor to the Provost for Global Scientific Initiatives at the University of Chicago.

Zierler:

When did your appointment as advisor to the Provost, when did that begin?

Kim:

Last fall.

Zierler:

And what do you do in that role?

Kim:

That's a very interesting question. I am trying to figure that out: what I'm supposed to do, and I would like to do. This is a new position and our goal is to advance the University’s global collaboration in the sciences and to support the community of international scholars and students at the University. But we do not have any specific program in mind. I will first have to look at various activities that our faculty has already been involved and then think about international cross-collaborative science initiatives, creating and sustaining international opportunities for faculty and students, and partnering to coordinate and enhance current capacities. I believe that stronger ties to different regions will also help us to understand the value of diversity and to strengthen our efforts of inclusion and diversity.

Zierler:

Young-Kee, before we go back to the beginning and develop your life narrative, I'd like to ask currently, in this time of the pandemic, what are some of the greatest challenges that you've had, both in your work as a physicist and with regard to your administrative responsibilities?

Kim:

There are many challenges, you know, but mental health for our students is one of my major concerns as the Department Chair at this moment. Our physics community consists of undergraduate and graduate students, postdocs, faculty and staff. Each group has its own challenges. For example, junior faculty with young children. They have to teach, to do research, to supervise students and postdocs in their research group, and to take care of their children. Our department have started several programs to help members of the department, but the situation is really tough.

As a physicist, one of my primary challenges last year was to handle a task that I led for the American community of particle physics as a chair of the Division of Particles and Fields of the American Physical Society. Early Spring last year, we launched a process called “Snowmass”. Snowmass is a year-long scientific study process, for the U.S. particle physics community to come together to identify a scientific vision for the future of particle physics in the U.S. and its international partners. We of course did not know the pandemic will last such a long time and we worked tirelessly virtually, hoping that it will end soon. In October last year, we had a community-wide workshop as part of Snowmass. If it were an in-person workshop, about 500 people would have come to the workshop. But with a virtual meeting, about 3,000 people attended it. Although in-person interactions are critical for Snowmass, many physicists who could not afford to attend an in-person workshop were able to attend it. For example, early career scientists and an international community. This virtual workshop provided equal access and became a more inclusive workshop. However, many people got exhausted by the end of last year and we decided to pause this process for about six months.

Zierler:

And Young-Kee, what about the science? The physics and the research collaborations you do? How much of this have you been able to continue virtually, remotely, and how much of it have you put on hold until we can get back to life as normal?

Kim:

Here, I am much luckier than many other scientists. I am an experimental particle physicist and my research heavily relies on very large particle accelerators and detectors, requiring a large number of collaborators. For example, I am a member of the ATLAS collaboration which has about 3,000 members from all over the world. Due to the size of the collaboration and physical distances between collaborators, we have been doing virtual meetings for a couple of decades. So, we have been well trained for virtual meetings. Of course, some activities such as detector development and construction cannot be done remotely. This pandemic resulted in delays in the overall experiment schedule.

Zierler:

There's a lot of data that you're able to analyze remotely.

Kim:

Correct. Data analysis and publication can be done remotely, and their schedules have not been affected much by the pandemic. However, this has been a very difficult time for our students and postdocs, especially those who do not have family nearby and have a very limited space without any social interactions.

Zierler:

Yet more reason to look forward to a vaccine and getting back to normal, right?

Kim:

Absolutely. Even data analysis can benefit a lot from in-person interactions. Things can get communicated much better in person.

Zierler:

Young-Kee, let's go all the way back to the beginning, starting with your family origins in Korea. First, I'd like to ask about your parents. Tell me about them and where they're from.

Kim:

I was born and raised in South Korea. In a small farm village, away from cities. My mother only got elementary school education and was a farmer. My father got high school education. He could not continue his study because he had to support his mother and three sisters. He had a decent job since his high school graduation but he had to quit when I was a middle school student due to his health. My parents have one son and five daughters.

Zierler:

When did you start to get interested in science? And what was available to you educationally to pursue those interests?

Kim:

As long as I can remember, I was always interested in math and fascinated by math. But science, I think it was when I was a middle school student. One of our science teachers asked me to attend a science competition, representing our school. He trained me and a few other students from the same school in the evenings. Subjects included physics, chemistry, biology, and geology. The first competition was conducted among students within a small region, like a county. Top students in this small region got further training and competed with top students from other small regions. The final step was a providence-scale competition. I ended up becoming the first prize winner.

Zierler:

Young-Kee, I'm curious if you think that had your parents had more opportunity, they would have pursued more education that they were able to attain?

Kim:

I believe so.

Zierler:

Do you have a sense that your mathematical abilities come from somewhere in your family? Even if that person might not have had the opportunities to attain an education tantamount to achieving their abilities?

Kim:

It's hard to say. But I know that my father, who passed away about ten years ago, remembered telephone numbers of all of his family, relatives, and friends and would always argue with a very clear logic. Speaking about my father, when he became nine years old, he thought that, "I have to go to the city and get educated." So he left home all by himself, age of nine (laughter). And he started supporting himself and get educated.

As I told you, I grew up with many siblings. Five girls and my parents shared one room. As you can imagine, the room was always noisy. If my sister complains that "It's too noisy and I cannot study,” my father would say, "Focus. If you do, you don’t hear any of this noise" (laughter). No excuse is allowed in our home. He was also interested in learning other stuff, singing, dancing, and playing musical instruments. He started taking these lessons when he was in his seventies, and he was extremely good at it (laughter). My mother is a very strong person, mentally and physically. She supported the entire family after my father quit his job and remained a keystone of the family. My mom has very interesting philosophy. She would say that I shouldn't learn how to do farming or housework. It is because if I am too good at it, I will end up becoming like her, a farmer and a housewife. She wanted me to become much more than that.

Zierler:

Young-Kee, as a window into South Korean culture, I'm curious as a girl and as a young woman, in pursuing your interests in math and science, were you ever made to feel discouraged? That this was not an appropriate area of interest for girls and women? Or was that not the case for you?

Kim:

Some discouragement came from people who were not very close to me, but I did not pay any attention to them. None of my family, my schoolteachers, my friends and my classmates discouraged me to become a scientist. However, my mother wished all of her girls to become medical doctors. It is because medical doctors are well respected in Korea and have no financial concerns. My high school was an all-girls high school and I liked it very much. I see that all-girls high schools have some advantages. Girls can learn all subjects without any discrimination or discouragement and they also have many opportunities to practice leaderships.

Zierler:

Is it common for high school to be separated by gender, or did you go to a special school?

Kim:

In Korea, most of high schools are separated by gender.

Zierler:

Young-Kee, I'd liked to ask more broadly. Was the threat of North Korean aggression, did that ever affect you personally? Did it ever affect the kinds of opportunities that were available to you or how you felt in terms of your own stability and security?

Kim:

I don’t think it affected me much. You know the story where two little pigs use a wolf-alert horn to play tricks on their brother, and this brother does not trust that trick after a while. It is like that. I grew up with so many threats of North Korea. Some are facts but there were many false alarms. After a while, we don’t pay much attention to them and it does not affect our daily lives much.

Zierler:

Are you aware of any family members that may have been separated as a result of the war and who you lost contact with, in North Korea?

Kim:

Yeah, my uncle, who was drafted for the Korean War, and he didn't come back. And his record got lost. So we don't know whether he is alive or dead, and we all assumed that he died during the war. But my grandmother would never accept that, and she'd always think that he would be alive somewhere, maybe in North Korea.

Zierler:

Young-Kee, coming from a rural environment but as a gifted student, what kind of opportunities were available to you for higher education when you were starting to think about university?

Kim:

So as a-- you mean as a junior high or high school student?

Zierler:

Right.

Kim:

There are two types of high schools in Korea. One is vocational high schools for those who want to get jobs right after graduation. The other type is for students who are interested in pursuing higher education. The latter prepares students for college entrance exams and my high school belongs to this type. Levels of students in these high schools are about the same because students are randomly assigned to these high schools and education among these schools is pretty much the same. There were two exams to enter a college. The first one was an exam given to all of the students who want to go to universities. The second one is specific to the universities which you apply for. Both exams play roles for getting an offer from a university. I don't know whether I answered your question.

Zierler:

Yeah. Yeah. And was your plan to pursue a degree in physics from the beginning, or you had a more general education at first, and then you landed on physics?

Kim:

My original plan was to major in math. But as I learned more about various scientific fields, physics looked very interesting. So, after the first year I decided to try physics. I thought that if physics did not work out for me I can always go back to math. I did not see this as a problem since I was confident about my math background.

Zierler:

Physics, of course, is a big world to jump into. What were the kinds of courses as an undergraduate that you felt you were best at?

Kim:

Quantum mechanics (laughs). To be honest, I was not a good student at all for the first two years in college. During these years, I did not pay any attention to classroom work. Instead, my interest was on Korean mask dance. This dance includes significant dramatic content reflecting the frustrations felt by the lower classes. I was really passionate about this dance and dramas. During my junior year, I thought seriously about my future directions and I started paying attention to classes. This was when modern physics and quantum mechanics were taught and I was fascinated by them, and that’s--

Zierler:

The rest is history, as they say.

Kim:

--how I became (laughter). That's right.

Zierler:

In those early years, did you know that you wanted to focus on the experimentation side of things?

Kim:

No. I had no experience on experiment until I came to the U.S. Because I liked math so much, my initial plan was to become a theoretical physicist. But in the graduate school, I had an opportunity to work on an experiment and I liked it very much. So I changed. I started with math, then theoretical physics, and finally experimental physics.

Zierler:

At what point did you realized that you wanted to pursue physics for graduate school? Was that right away or that came later on?

Kim:

I think it's- around my senior year? This is when I had to make a decision on my future. Either getting a job or going to a graduate school. I concluded that I wanted to go to a graduate school, not in Korea but in the U.S. But I was not prepared to apply for U.S. universities. I did not take TOEFL and GRE by then (laughter). So I decided to join a master program in Korea and to prepare for graduate application during the master program. And that is what I did.

Zierler:

And Young-Kee, I'm curious. Did you receive advice from your mentors that in order to reach the pinnacles in physics, that you would be best-served leaving Korea and pursuing a degree in the United States?

Kim:

Absolutely. I had an amazing teacher, Professor Joo Sang Kang. He taught modern physics and quantum mechanics and he completely opened my eyes. He became my master thesis advisor. He got his PhD in the U.S., and certainly I have good information from him. Most of other professors in our department also received their PhDs in the U.S. One of my professors got his PhD at the University of Rochester that I ended up going to.

Zierler:

How widely traveled were you before you got to the United States, before you got to Rochester? Had you left South Korea before?

Kim:

No, not at all. In fact, I went to Japan before I came to U.S. The Korean academic year ends in February and the U.S. academic year starts in August, and so I had a few months between my master program and the PhD program at the University of Rochester. Professor Olson from Rochester approached me and said that if I want, I could go to Japan for a few months working on the particle physics experiment, called “AMY”. This was an amazing opportunity for me, despite that I was planning to pursue theoretical physics, and I immediately said yes. So I went to Japan in April, 1986, and from there, to Rochester in July, 1986. In Japan, I joined a team who constructed a major detector device for the AMY experiment, and I enjoyed my work very much. This was a crucial element for me to become an experimental physicist.

Zierler:

And how was your English when you got to Rochester?

Kim:

Before I left Korea, I managed to get a bare minimum TOEFL score that's required to get admitted to a U.S. university, but this is far away from my communication ability in English. The fact that I spent about three months in Japan helped me a lot, since most of collaborators of the experiment were Americans. But three months was not enough for me. I had a tough time in Rochester. You know, professors came from all over the world and some had very heavy accents. I just couldn't handle it very well. But it was very nice that many professors put copies of their lecture notes in the library. These lecture notes were tremendously helpful.

Zierler:

Young-Kee, you got comfortable in Rochester, and you started to understand the lay of the land. Did you find it to be a welcoming place?

Kim:

Yeah, very much so. Rochester is a small private university. The department had a very welcoming environment and I felt that everyone in the department was extremely kind to me and wanted to help.

Zierler:

How did you go about developing a relationship with your graduate advisor?

Kim:

I had an outstanding graduate advisor and mentor, Professor Steve Olsen. Although I enjoyed working on the experiment for a few months in Japan in 1986, my interest in theory did not go away. But Steve continued to provide me information on progress that the collaboration has made on the experiment. He offered me a summer position in 1987 and after that summer, I decided to be his student. I'm really lucky to have people like him around me.

Zierler:

How did you go about developing a dissertation topic?

Kim:

Gee, I haven't thought about that (laughter).

Zierler:

It wasn't accidental. You had to come up with something.

Kim:

Yeah, yeah. My initial focus was on operating and calibrating detector components and fixing or improving them. And I did not worry or think about a thesis topic. So I just dived in working on the detector and had much fun. One and a half years or so later, I started thinking about a physics topic for data analysis. That is, my thesis topic. Certainly Steve and I discussed a lot about physics that the AMY experiment could enable. I chose one that I was interested in working on based our numerous conversations. I hope my memory is correct (laughter).

Zierler:

That's fine. And Young-Kee, to zoom out a little bit, when you were a graduate student, and you're thinking, you know, not only about the academic things that are most exciting to you, but more broadly in thinking about your career, the kind of research to pursue that would be useful for pursuing an academic career. What were some of the most exciting things in experimental particle physics that were going on at that time?

Kim:

Well, at that time, key interests of the particle physics community were discoveries of particles including the top quark, the Higgs boson, and supersymmetric partner particles. The theory could not predict their mass values but particle physicists postulated that their masses are high and this resulted in a race among various regions to build higher energy accelerators. Our AMY experiment was using an accelerator, called the TRISTAN, a collider accelerator of an electron beam and its anti-particle positron beam. The TRISTAN was the highest energy electron-positron collider at that time.

Unfortunately, no new particles were discovered by our experiment. The top quark was discovered by the CDF and Dzero experiments with the Tevatron accelerator at Fermilab in 1995. It turns out that the top quark mass is much higher than what many scientists had imagined. The Higgs boson was discovered by the ATLAS and CMS experiments with the LHC accelerator at CERN in 2012. We haven’t seen supersymmetric partner particles.

Zierler:

What did you see as your central conclusion in your thesis research?

Kim:

My thesis topic was to study and test Quantum Chromodynamics via properties of quarks and gluons. Quarks are building blocks of the universe and gluons are force carriers of the strong force that confines quarks into protons and neutrons. My thesis results were one of the first experimental comparison between quarks and gluons.

Zierler:

Besides Steven Olsen, who else was on your committee?

Kim:

Good question (laughter). The committee, gee. I cannot remember their names except my advisor. I am very embarrassed by this. Concerning the committee, in addition to my advisor and two physics professors who did not work very closely with me, I had one professor from the Chemistry Department. The department policy was that one committee member should be outside of the Physics Department to give a bit more broader perspective. I vividly remember two comments from the committee at the end of my thesis defense. One was from this chemistry professor. He said to me, "Please don't go back to Korea. I want you to continue your research." (laughter). He was worried that if I go back to Korea, go back to the Korean society, I might give up my research, and end up supporting the family. He had a female Korean student in the past and she went back to Korea and that was the end of her research. The other one was from my advisor, Steve Olsen. He said that, "you'll make me famous" (laughter).

Zierler:

No pressure, right? Young-Kee, that's exactly the question I wanted to ask. When you decided to come to Rochester, from Korea, was your initial momentum or your initial assumption that you were going for your graduate work, but that you would be going back to Korea?

Kim:

Absolutely.

Zierler:

At what point did you-- So really, you thought that you would not be making a life for yourself in the United States, and it was only as a result of this formative relationship and this encouragement that you decided to commit to pursuing a career State-side?

Kim:

When I left Korea, I assumed that after a PhD, I would come back to Korea. If I succeed getting a PhD, I may get a position in Korea in a university. In fact, becoming a university professor in Korea was the best I could hope for. While completing my PhD, I understood about a postdoc, another layer between a PhD and either a lab scientist or a university professor. I didn't know about this postdoctoral layer before. So naïve. With a lot of encouragement and support from my advisor and other scientists whom I have collaborated with, I applied for a postdoc position in the U.S. After some years as a postdoc, I realized that I had to find a job. I applied for faculty positions in U.S. I was very lucky that I got offers. I tend not to think much beyond my current work and the very next step. Just one at a time and one thing led to another. This is how it ended up here.

Zierler:

After you defended, Young-Kee, what were the opportunities that were available to you in terms of postdoc positions?

Kim:

I had several postdoc opportunities, you know, staying in U.S., or going to Germany. But I chose to stay in U.S. I chose Lawrence Berkeley National Laboratory.

Zierler:

And who was it at Berkeley that you wanted to work with?

Kim:

Berkeley had an excellent group of experimental particle physicists. Their vibrant atmosphere excited me. The group got strongly involved in new detector design and construction and in various physics analyses. So, it's not one person, but what they do and who they are collectively. I visited various institutions in U.S. and in Europe before I made my decision. I learned a lot about what various institutions do, what kind of environment they have by visiting them.

Zierler:

Did you see your postdoc at Berkeley as an opportunity to pursue new physics, or did you see this as an opportunity to expand and improve upon your thesis research as a graduate student?

Kim:

The experiment that I chose to work on is different from my thesis research experiment. My thesis research was done in Japan using collisions of electrons and positrons, while my postdoc research was done in U.S. using collisions of protons and anti-protons. This proton anti-proton collider, called the Tevatron, was located at Fermilab near Chicago. Incidentally, I could have joined a research group in a German institution to work on collisions of electrons and protons in Germany. Although these are all particle colliders, there are substantial differences among them in terms of scientific outcomes and technical challenges. I was very sure about choosing a different experiment from my thesis experiment. I wanted to have a different experience.

Zierler:

And in what ways was that advantageous for you? In terms of broadening your research agenda.

Kim:

You know, I wanted to learn various areas of particle physics. Yes, it was advantageous for me by broadening scientific and technical knowledge.

Zierler:

Well, Young-Kee, I'm looking at the clock right now and this is a good place to hit pause and we'll return later today.

Kim:

Okay, why thank you.

 

[End Session 1]

[Begin Session 2]

 

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is later in the day on January 5th, 2021. I'm so happy to be back with Professor Young-Kee Kim. Young-Kee, for my first question on our second session, I'd like to ask to sort of set the stage for your postdoc at Lawrence Berkeley, had you had exposure to a national laboratory environment prior to coming out to Berkeley?

Kim:

Not a national laboratory in the U.S., but a national laboratory in Japan. While I was a graduate student, I worked on the AMY experiment, located at a Japanese national laboratory, KEK. However, I didn't know any details on the nature and structure of national laboratories. I knew that national laboratories are needed to build and operate big and complex facilities such as accelerators and detectors for particle physics research. I didn't know much more than that.

Zierler:

And I'm curious. In 1990, this is really right in the middle of the excitement surrounding the possibility of the SSC (Superconducting Super Collider). Were you following that at all?

Kim:

In 1990, my plate was full and did not know much about the SSC. I was completely immersed in my thesis experiment and data analysis between Summer 1987 and Spring 1990 in Japan. In 1990, I finished my thesis research project, wrote my thesis, came back to U.S. to defend my thesis, traveled around in Europe and moved to Lawrence Berkeley National Laboratory to start my postdoc work. Only when I started my postdoc position at the end of 1990, I understood more about the SSC.

Zierler:

And this very formative advice you got from your mentors to stay in the United States, or they encouraged you, "Don't go back to Korea, there's so much that you could do if you stay in the United States." How much of that was sort of general advice, that for your field, the place to be was the United States, and how much of that was specifically, "Stay in the United States and go to Berkeley Lab because that's really the best place for you to go onto the next things that you want to do"?

Kim:

I think it's the combination of the two. Korea did not have a lot of opportunities for me back then. My research field requires large particle accelerators which were located at Fermilab in the U.S., CERN in Europe, and KEK in Japan. Although Korean institutions participated in experiments with particle accelerators, there were more opportunities being in the U.S., Japan or Europe. Since I had already had experience in Japan, I wanted to be somewhere else, either the U.S. or Europe to gain broader experiences.

Zierler:

To the extent that you self-consciously wanted to get out of your comfort zone from graduate school and pursue new physics, as you were doing that, what did you discover about your talents that you might not have known before?

Kim:

Certainly. I learned that to answer some of the profound questions in science we need large facilities which can only be realized by a large group of talented people with various expertise and training. I also realized that I very much like collaborative work. I saw beauty in it. How diverse talents and opinions could make the entire program much stronger and more successful. People from different backgrounds and training produce better science. Very important lesson.

Zierler:

Was it a six-year appointment, or did you have a three-year appointment at Berkeley Lab, and you renewed?

Kim:

I believe so.

Zierler:

And in sum, Young-Kee, what do you see as your most significant work while you were at Berkeley Lab?

Kim:

As a postdoc, I worked on the CDF (Collider Detector at Fermilab) experiment at Fermilab near Chicago. The CDF collaboration with a few hundred members built a detector and installed it around the collision area of a proton and anti-proton collider called the Tevatron. The CDF has operated for about fifteen years before I joined the experiment. Big efforts were going on to upgrade the detector and accelerator when I joined the collaboration. I was deeply involved in the detector upgrade project, especially a detector component, called calorimeter, that measures energies of particles produced from proton-antiproton collisions. I would say that this is one of my main accomplishments. With the upgraded detector and accelerator, we took data for a couple of years and I used this data to measure the mass of the W boson, one of carriers of the weak force. The weak force is responsible to radioactive decays. If we measure the mass of the W boson and the mass of the top quark very presicely, we can predict the mass range of the Higgs--

Zierler:

Yep.

Kim:

--boson, the one responsible for giving masses to all elementary particles, building blocks of the universe. My work to measure the W boson mass continued when I became assistant professor at University of California, Berkeley. More and more precisely measured. After that, I started to focus on measuring the mass of the top quark precisely.

Zierler:

Young-Kee, I'm curious if you've looked back. Do you see any logic or intellectual advantage to starting in graduate school with the strong forces in particle physics and then going on to the weak forces? Is there any logic to that that might have been advantageous for your overall research and education?

Kim:

Well, first, I wanted to do something different. But most importantly, I got so excited about understanding the origin of mass for elementary particles. This is one of the most central questions in particle physics.

Zierler:

Young-Kee, I'm curious if you had interactions with the faculty at UC Berkeley that were useful when you were thinking about going on the job market, and ultimately, your decision to join the faculty at UC Berkeley?

Kim:

I had a number of senior particle physicists from various institutions who are my strong supporters. I was lucky to have these people around me. They are members of the CDF collaboration. This is a benefit of working in a large collaboration. Actually, I was quite naïve and did not think much about the job until the very late stage of my postdoctoral period. (laughter).

Zierler:

Meaning that if you just follow what you're doing, and you're really working well in that field, the opportunities will make themselves available?

Kim:

Something like that.

Zierler:

And so were you specifically on the job market? Or were you just doing your research and then the faculty recruited you to join?

Kim:

I just applied for positions that were available.

Zierler:

The research on the top quark, of course, was a major national and international collaboration. Who are some of the key people that you were working on for this research?

Kim:

Too many to list because there are many research projects about the top quark, ranging from the discovery of the top quark to observations and measurements of various top quark properties. Each analysis is usually done by a group of people.

Zierler:

Young-Kee, what were some of the difficult transitions, since you were still in an experimental mode, in going to a faculty and no longer being all the time in a national laboratory environment?

Kim:

As a postdoc, my primary focus was my own research. As a faculty member, I had to do multitasking. Responsibilities include teaching, building my own research group, advising my students and postdocs to do their research, and conducting my own research. So, it is a big transition. Teaching undergraduates was tough for me. I haven’t taught before and so a lot of preparation time was needed. In addition, I had to overcome language barriers and culture barriers. For example, expectations from U.S. students are quite different from those of Korean students. In Korea, there were more separation between professors and students.

Zierler:

Hierarchy.

Kim:

Yeah, there were a clear top-down structure. Not much discussions in classrooms. The U.S. system is more horizontal, which is better for both education and science. Ah, time to time I was mistaken as a Teaching Assistant. Students did not expect that someone like me, short Asian woman, could be a physics professor.

Zierler:

Did you take on graduate students right away?

Kim:

Yes, but it took a couple of years to build my research team.

Zierler:

Young-Kee, would you find yourself spending a lot of time at CERN, or were you relying on your collaborators who were more local in Geneva?

Kim:

While I was working on the CDF experiment as a faculty member at UC Berkeley and U.Chicago, I traveled to Fermilab very frequently. It takes about 8 hours from Berkeley to Fermilab and only about 1 hour from Chicago to Fermilab. With the ATLAS experiment at CERN, I was able to travel only a few times a year, and for each trip, I stayed a couple of weeks to a couple of months. But since I became chair of the department, I don't have that luxury

Zierler:

Sure.

Kim:

Most of my research group is stationed at CERN. So, many of discussions with my students and postdocs have been taking place via video meetings. My main role now is to advise and guide my team. Real work is being done by my students and postdocs.

Zierler:

And how well-developed was the ATLAS project by the time you joined?

Kim:

It was very well-developed by the time I joined. My original plan was to join ATLAS much earlier. I mean, you know, I was a co-spokesperson of CDF experiment between 2004 and 2006, and I was planning to split my time between CDF and ATLAS, 50/50 from 2006. But even before my co-spokesperson term was over, I was asked to be deputy director of Fermilab.

Zierler:

Because you weren't busy enough, right? They wanted you to do more (laughter)

Kim:

Yeah, right.

Zierler:

Young-Kee, did you see your dual collaboration with CDF and the ATLAS experiment as mutually beneficial? In other words, your work on ATLAS was useful for CDF and your work on CDF was useful for ATLAS? Or did you tend to sort of separate that work out intellectually?

Kim:

Absolutely. My CDF experience has been tremendously helpful for my ATLAS work. At the same time, ATLAS was needed for my CDF group. For example, one of my postdocs who worked on the top quark mass measurement with the CDF data needed hardware experience. With the CDF experiment ending, CDF did not have any hardware project, but the ATLAS experiment provided a great opportunity for him to work on hardware.

Zierler:

What were your reactions when the Tevatron shut down? Both academically and perhaps even emotionally?

Kim:

Academically, it was the right thing to do. Emotionally it was very sad.

Zierler:

It was time?

Kim:

Yeah, it was. The LHC was a brand-new collider and its energy is much higher, thus much more powerful for producing science, than the Tevatron. The Tevatron, after three decades as the highest energy accelerator, would have to shut down when the LHC became operating. The LHC turned on in 2009. Usually "turning on" is not a step function, but it takes a couple of years for a machine like LHC to fully function as a stable accelerator. So, turning off the Tevatron in 2011 is the right time. Of course, emotionally, it's, you know, it's like moving your house. Even if your new house is bigger and better, moving away from all of your memories and your history is a sad thing, but you know, we have to move on.

Zierler:

Were you concerned for Fermilab's future after Tevatron? Did you see a clear path forward in terms of what the lab could accomplish after Tevatron?

Kim:

Yes, that's what I've done when I was appointed as deputy director of Fermilab in 2006. My primary task was to make a strategic plan for the long-term future of the lab, through 2020’s and 2030’s. The process started with input from particle physics and accelerator communities, not only the U.S. community but also the international community. We finalized our plan and it was to switch from the Energy Frontier, such as Tevatron and LHC, to the Intensity Frontier, such as neutrino programs and muon programs.

Zierler:

Young-Kee, so I understand both the chronology and your motivations of moving from Berkeley to Chicago, was Fermilab part of the plan from the beginning? Did you know that moving to Chicago meant that you were going to be at Fermilab physically on a more permanent basis? Or was that sort of a separate consideration that came after your appointment to the faculty in Chicago?

Kim:

Right, so like my previous career paths, my decision was simply based on my research and life at that time. I had not thought about potential future positions such as co-spokesperson of the CDF experiment and deputy director of Fermilab, that required my presence at Fermilab.

Zierler:

Were you looking to move or were you specifically recruited?

Kim:

I was recruited. And the decision to move was related to my love life (laughter). I met my husband while I was faculty at UC Berkeley, and he was, well still is, a professor at University of Chicago. We got married in October 2002. We wanted to work in the same place.

Zierler:

And you accepted upon yourself the two-body problem.

Kim:

That's right. Berkeley tried to recruit my husband to Berkeley, and Chicago recruited me to Chicago, so we are in a good situation that we had options. There was a third one. An institution in the Boston area also wanted to have both of us. We chose U. Chicago. U. Chicago is a great institution and the proximity to the Tevatron, then at the top (laughter) as a particle physics facility, was advantageous for my research. Berkeley is a great institution, and I loved it, but I also wanted to challenge myself going to a new place and learning new stuff. It was a good move after all to balance between work and life for later positions as co-spokesperson of the CDF experiment and deputy director of Fermilab. Speaking about that, when my collaborators nominated me for CDF’s co-spokesperson, I felt a real shock. I did not even dream about leading more than 600 amazingly talented people. Every member had one vote and I got elected surprisingly (laughter). One thing led to another. The next thing I knew was that I was asked to be deputy director of Fermilab.

Zierler:

Young-Kee, administratively, both as spokesperson and as deputy director, did you find, and this is a question relevant even to today, as your term as chair of the department. What strategies have you employed to ensure that your administrative responsibilities don't pull you away from the physics entirely?

Kim:

My strategy is getting outstanding students and postdocs. They have been the ones who have pulled me back to physics all the time. They also helped me to do my job better as CDF spokesperson, Fermilab deputy director and Physics Department Chair. It is because through them, I understand much better about concerns that people at various levels have. They have been connecting me to the real world so that I would not be isolated from real issues (laughter).

Zierler:

Young-Kee, I'm curious as deputy director, if that gave you a window onto the Department of Energy and science policy in Washington more generally?

Kim:

Yeah. I learned a tremendous amount about the Department of Energy and some about science policy in Washington.

Zierler:

I'd like to ask a question that's more philosophy of science than it is science itself, and that's moving ahead to CERN and the discovery of the Higgs. As I'm sure you're aware, there's a sentiment in the scientific community that tends to downplay the significance of the discovery of the Higgs because theoretically, as they say, we knew it was there, right? Of course, you've heard this line of thinking before. Generally, what is your reaction to that?

Kim:

I would say that the discovery of the Higgs closed one chapter and opened a new chapter in science. Yes, the theory, called the Standard Model of particle physics, indeed predicted the Higgs. Thus, the discovery of the Higgs is a testament to the success of the theory. However, this theory has so many holes, and there are so many things that this theory cannot answer. The Higgs is really opening a big chapter, a window for us to see how we should tackle these bigger questions. Detailed study of the Higgs may shed light on solutions to these questions.

Zierler:

And Young-Kee, what are those bigger questions? Once we see the Higgs, what new questions are we able to even ask that were not possible before the discovery?

Kim:

Concerning big questions, let me list a few. What is the nature of dark matter? Effects of dark matter have been observed in the universe numerous times. Why is the current universe dominated by matter particles? In another word, what happened to anti-matter particles that existed in the early universe? Why neutrinos behave the way they do? Why is the top quark so heavy, a million times heavier than the electron? The Higgs is responsible to give masses to the top quark and the electron, but the currently theory cannot explain specific mass values. Why are there six quarks and six leptons? Who ordered them? Why are there four forces in the universe? Will these four become one at a very high energy regime or at the very beginning of the universe?

There are various new theories that can address some of these questions. By making precise measurements of Higgs properties and comparing them with what these theories predict, we may be able to discover a new and better theory, then the Standard Model.

Zierler:

Young-Kee, from the outside looking in, of course, the announcement of the discovery of the Higgs was so dramatic, right?

Kim:

That's right.

Zierler:

It was headline news. But from your perspective, from the inside, do you see the discovery as more of a gradual process, where the data had to continually be refined and understood? Or was it even from your perspective, was it dramatic and did it happen quickly?

Kim:

First, I would like to say that scientific knowledge is accumulative. We have a tremendous amount of knowledge produced by many generations of scientists. The discovery of the Higgs is based on this accumulative scientific knowledge, combined with new tools, the LHC and its ATLAS and CMS experiments. We kind of saw this discovery coming based on the results from the Tevatron’s CDF and DZero experiments. The CDF and DZero’s measurements of the W boson mass and the top quark mass predicted a range of the Higgs mass. In addition, the Tevatron’s Higgs search results saw a little bit of a hint of the Higgs. But the Higgs discovery by the LHC at CERN is very dramatic. It was huge.

Zierler:

I'm curious because CERN is such an international collaboration by definition, but there is also a sense in the United States that what the Higgs discovery really represented was, that the mantle of leadership in high energy physics had transferred from the United States to Europe. Was that your sense as well?

Kim:

The U.S. used to host the highest energy facility, the Tevatron, for three decades and the Energy Frontier facility has moved to Europe. However, scientists who work on this physics are from all over the world. U.S. scientists are about twenty-five percent to thirty percent of this community and this is a substantially large number. So, U.S. has a strong intellectual leadership. I think the U.S. still has a capability of bringing the Energy Frontier facility back to U.S. if we have enough money in this research.

Zierler:

Well, we have the money. Do we have the political willpower is the question.

Kim:

It is true that political willpower is important and that is the question. I want to note that future Energy Frontier facilities will be global scales, and global contributions and collaboration will be required to make them a reality.

Zierler:

Meaning what you're saying is that it's not really so useful to be thinking in national kinds of terms.

Kim:

Exactly. Colliders for particle physics are global projects. To make it work, not only the intellectual contributions from physicists and engineers around the world but also financial contributions are important.

Zierler:

Young-Kee, this is sort of a general question, because you've been involved over the course of your career in many different ways with the National Science Foundation. So generally, what has been valuable to you personally, and for your field, with regard to your involvement with the National Science Foundation?

Kim:

Currently my research is supported by National Science Foundation. I used to work with the DOE which is a more mission-oriented organization. In contrast, the National Science Foundation is based more on individual PIs. But they also must have strategic thinking about the big questions confronting particle physics. So, their philosophies is somewhat different. I think that's very valuable to have both kinds of agencies. They complement each other very nicely.

Zierler:

I'd like to ask on the teaching side of things, obviously now you're comfortable teaching. You've come a long way from your first attempts at doing this at Berkeley. At Chicago, what are your favorite classes to teach undergraduates?

Kim:

Electromagnetism.

Zierler:

Why?

Kim:

Let me try to answer this by referring to my recent research work on accelerators. Electromagnetism is key for accelerators. So, here is connection. Incidentally, accelerators are essential not only for discovery science but for medicine, industry and society. Their impacts are huge, and they could be even much bigger with scientific and technical breakthroughs. For these breakthroughs, we need more brains in this field. However, we only produced about 20 PhDs per year in US, 2-0, for the entire (laughs) US. That is clearly not enough.

Zierler:

This is way too low, you're saying.

Kim:

Yes, for example, many thousands of scientists use accelerators for their science research and many hundreds of students from these fields receive their PhDs every year. Their research is limited by accelerator capabilities. More accelerator students and more accelerator scientists would make a big difference. Because of this, I started paying attention to accelerator physics education and training. I started my accelerator group by collaborating with accelerator physicists. Going back to your earlier question, if you look at accelerator science, it is mostly about electromagnetism (laughter). So, it is connected to what I like to teach.

But also electromagnetism is a good example of what we try to do in particle physics. That is, the unification of four forces. Maxwell's equations brought a unification of electricity and magnetism. This is similar to what particle physicists are interested in trying to find a unified force: maybe one force in the end, instead of many. The concept is similar. It also shows a bit about how science is done: one generation builds on the work that came before. Maxwell's equations were not only his own. He put together many generations of work and discoveries. With his synthesis came the ability to explain light! So overall, it is a very beautiful and interesting topic (laughter).

Zierler:

And for your graduate students, Young-Kee, to the extent that the next generation that's up and coming, both in terms of the kinds of advice you give them on the things that they ought to concentrate on or work on, and their own interests, what might your current crop of graduate students tell us about where the field is headed?

Kim:

That’s a profound question. I encourage my students to think about the key questions in the field and what questions they'd like to answer, before choosing thesis topics. I would like them to convince me that they have strong motivation and that the topics can have scientific impact. I am okay even if they choose topics that are somewhat different from my own interests. So far, this process has worked out well. One interesting observation is that our students are thirsty about discovering something (laughter)

Zierler:

That's good.

Kim:

During my early career period, I was interested in measurements, such as measurements of the W mass and the top quark mass. Those measurements were important for predicting the Higgs mass. Not only that, but also, they could shed light on new physics if there was a mismatch between the predicted Higgs mass and the Higgs mass measurement. So, I was interested in new physics, but did it through precision measurements. These days, I find that many students would like to go after new physics more directly. As I mentioned earlier, there are many unanswered questions and discoveries could come in many ways.

Zierler:

What you're conveying clearly is that there is fundamental work to be done, and there is decades’ worth of research to get there. That's coming across clearly.

Kim:

Yeah. More than decades (laughter).

Zierler:

Yeah. Young-Kee, we've already brought the narrative up to the present in terms of the science. I'd like to ask you, sociologically, in your capacity as chair, as a woman and as an Asian, you know this year, 2020, in the United States has been a year of racial reckoning. And STEM and physics has dealt with these issues as well. I'm curious what opportunities, if any, you've seen to promote diversity and inclusivity in your role, in your position of authority as chair at a tremendously important physics program that sets the tone beyond Chicago? In terms of how the larger physics community deals with these things.

Kim:

I have several roles. One is chair of the physics department, and I was chair of Division of Particles and Fields of the American Physical Society. I mean, the equity, diversity and inclusions issue is something that I thought a lot about. So, since I became department chair in 2016, here at the university, I had a lot of new initiatives, at many levels – from some are even goofy stuff or social events to more system-wide initiates. I've tried a lot of things. So, this effort has been going on for a number of years.

Now, in the year 2020, what I noticed is, as you said exactly, an awakening. Especially in the younger generation. We have a very proactive group in our department. They were self-motivated, and they want to do something. They proved a lot of feedback about what doesn't work and what has to be improved. They bring a lot of good ideas and we execute them together. It is remarkable. I see a similar thing within the Division of Particles and Fields in the APS. I really hope that our enthusiasm and efforts shown in 2020 will continue and result in a big change in our system and our culture.

Zierler:

It's a hard question to answer. There's no doubt about it. No easy answers. Young-Kee, I'd like to ask. You know, looking over your accomplishments and your collaborations and associations, it's hard to think of a person more qualified than you to be in your position as advisor to the provost for global scientific initiatives. I mean, you really have partnerships everywhere. Every continent on Earth, you're involved in some way or another in the physics. I'd like to ask. You know, because this is such a new position for you, what do you see as the most efficacious way to leverage all of these connections and collaborations that you've built, and to what end specifically, both in terms of furthering the scientific mission of the University of Chicago specifically, and also more generally, furthering the spirit of collaboration upon which modern science and even big science is dependent?

Kim:

Advancement in science is often conducted on global scales, involving multiple countries and hundreds to thousands of scientists and engineers. The LHC is a great example. By leveraging knowledge and resources, sharing costs, and generating innovative ideas and solutions by collaborators from different training and backgrounds, I believe that global projects can make progress the fastest. This all sounds good, but of course, there are many challenges. Every country has their own culture and rules. Bringing them together demands big coordination and management challenges. It sometimes takes a long time to resolve all of the differences. As you pointed out, I was involved in activities internationally and played a lot of advisory roles for institutions in various countries and continents. They are very, very different, socially, historically and politically (laughter). I believe that the best way is to keep finding scientific connections among various groups from different regions and to practice collaboration. By doing so, trust can be built and stronger collaboration can be established.

Zierler:

Of course, of course.

Kim:

Science could help connect us -- science without borders is much like music without borders. The scientific benefit from working together is huge. From my advisory roles in some countries, I saw some societies are rather closed, and if they could open and learn how to connect with others, there would be so much benefit. I just wish the world to be more open. And peace on Earth (laughter). The culture of some of the countries is still rather hierarchical and less inclusive. I would like to have positive elements from some regions in the world shared by other countries.

Zierler:

Of course.

Kim:

Of course, U.S. has a lot of issues and there is a lot to improve, but compared to many other societies, it is quite open. I am very thankful to US and I have a big debt to the American system. I came to US. I got educated, and they paid for me to learn! A person like me could come in and take important roles.

Zierler:

You're saying that the American model has much to offer the world.

Kim:

I do really believe so.

Zierler:

Young-Kee, for my last question, looking to the future, you've already conveyed how much fundamental work there is to do for your graduate students, for the next generation, even well into the next century. That does beg the question for you. Your administrative opportunities are always going to be there, but what I'd like to ask is for you, in terms of the science, in terms of the physics, what's most compelling to you as you look forward to the next chapter in your career? What are the things that you want to be involved in personally for the remainder of your time as a physicist?

Kim:

I want to continue to my research work of studying the Higgs boson. Higgs could be an amazing tool to discover new physics. My current interests are how Higgs interact to itself, whether Higgs is related to mass of the dark matter particle and whether Higgs will give a hint to explain why the current universe is dominated by matter particles. Addressing these questions may require accelerators that are much more powerful than the LHC. These new accelerators will be mega-scale projects, demanding even more global contributions and participation. Our international particle physics and accelerator communities have been discussing these possibilities.

Zierler:

Well, Young-Kee, it's something certainly to stay tuned for and good luck in the endeavor. I hope you're successful.

Kim:

Yeah, I hope so, too (laughter).

Zierler:

Young-Kee, it's been a delight spending this time with you. I'd like to thank you for doing this. And your comments and recollections over the course of your career are so important for the historical record, so I'm so deeply appreciative that we were able to connect. Thank you so much.

Kim:

Thank you so much.