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Thomas Cormier’s Interview

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Thomas Cormier is a nuclear physicist who leads the Large Hadron Collider Heavy Ion Group at Oak Ridge National Laboratory. In this interview, Cormier describes how he became interested in science at a young age. He then discusses his work at the Large Hadron Collider at CERN, the European Organization for Nuclear Research, on experiments such as ALICE (A Large Ion Collider Experiment). Cormier underscores the importance of such testing, explaining how it offers insight into the formation of our universe. He concludes by describing future plans for the construction of even larger particle accelerators and the scientific and societal challenges involved in undertaking such endeavors.

Date of Interview:
April 25, 2018
Location of the Interview:


Cindy Kelly: I’m Cindy Kelly, Atomic Heritage Foundation. It is Wednesday, April 25, 2018. I have with me Tom Cormier. First question is please say your full name and spell it.

Thomas Cormier: Tom Cormier, C-o-r-m-i-e-r.

Kelly: Perfect. Okay, my first question to everybody has been to tell me a little bit about yourself, where you’re from, when you were born, your education and how you came to be a scientist.

Cormier: I grew up in the suburbs of Boston in the town of Lexington, which is a very historic area in its own right. Growing up there, I was surrounded by people who in that community lived and worked in and around Boston in many of the big universities in the Boston area. In fact, a lot of the neighbors on my street were from MIT [Massachusetts Institute of Technology] and so forth.

My father, who was very interested in science but was not a scientist – he was kind of an engineer, a hands-on sort of a guy. He always talked about physicists, even when I was very young. Because he grew up, of course, through the period where, from his perspective, physicists helped with the existential crisis of World War II. So he was very impressed with physicists, and he would always talk to me about them. Although he really understood almost nothing from a fundamental point of view, he really wanted to hear about it all the time. I sort of researched things. I can remember even being very young researching things and trying to help explain it to him.

Finally, when I got older, I just went to my neighborhood school, which was MIT. And the rest is sort of history. By the time I arrived at MIT – which was 1967 when I first arrived there – every significant university in the United States had a burgeoning program in nuclear physics already. It was something that also grew out of the Manhattan Project. It had sent its roots into the university system in the United States. Virtually every university in the United States of any size had its own particle accelerator in those days. As an undergraduate, you were invited to get your hands into the physics and work with these machines that were all over the place.

Of course, over the years, those machines were turned off gradually, and the science got bigger and bigger and bigger. Until finally, you don’t find the kind of science we do anymore on a university campus, that’s for sure. The science has sort of outgrown that. But I’ve been attached to it right from those early days.

Kelly: What happened next between MIT and ORNL [Oak Ridge National Laboratory]?

Cormier: I had the usual few post-doc positions. I spent a year in Germany at the Max Planck Institute. Then I got my first faculty position and, as often happens to young assistant professors, the way you get promoted is by moving to another university. I had tours of duty at several places, until finally I had become a senior professor and got invited to join the faculty as a department head. Worked as a department head for a number of years, until finally a position opened up here for a new group leader to give the effort in the kind of physics that I was doing, called heavy ion physics. I’ll have to explain why in a bit. But there was an opening for a leader in that area here at ORNL to rejuvenate the effort and give it a new focus, and so I thought it would be interesting.

I was, at the time I came here, probably officially past the retirement age, let’s say. I was looking forward to working for, whatever, five, six, seven years or so and taking this challenge of instituting a new program and seeing what we could do with it.

Kelly:  How many years has it been?

Cormier: It’s been five years so far. I would say we really accomplished most of what we set out to do in that period. I’ve hired a lot of new people and built up the group, as you know, at CERN [European Laboratory for Nuclear Research], and got the necessary rules waived to allow us to site our people at CERN. The group, literally, is in Geneva, Switzerland, although I’m here most of the time. One week a month, roughly, I go to Geneva.

Kelly:  Can you describe in very simple, layman terms what it is that your group is involved in?

Cormier: Right. We use the Large Hadron Collider at the CERN facility. CERN is the European Center for Nuclear Research, and all the European countries come together there to conduct their research in this field, elementary particle physics and high energy physics. By pooling their resources, they’re able to build an impressive facility, a world-class facility. It’s said to be the largest physics laboratory in the world. Today, not only Europeans come there, but also a very substantial number of Americans, for instance, and Asians come there to do their work.  

The kind of experiments that are mounted on the Large Hadron Collider typically have thousands of collaborators. The ALICE [A Large Ion Collider Experiment] experiment that I’m part of has about 2,000 collaborators. That is, when we publish a paper, it has 2,000 names on it as the authors of the paper. It’s a significant undertaking. The other experiments are even larger than that. In fact, there’s some that are approaching 5,000 authors, I think.

It is definitely Big Science. Obviously, this doesn’t fit on a university campus anymore. In fact, it almost doesn’t fit in more than one place in the world. The whole world comes together to do this in one place, and that’s what CERN is.

At this facility, what we do is we collide elementary particles. My specialty is colliding whole nuclei. Whole lead nuclei, circulating around this accelerator in opposite directions at really unprecedented energies, are brought into collisions as a means to produce tiny samples of ordinary matter, heated to trillions of degrees Centigrade and compressed to hundreds of times the density of normal nuclei, to essentially turn back the clock. This tiny sample of matter is similar to, it turns out, what the matter that made up the universe was like when the universe was only a few microseconds old. Basically, using that facility, and those special ions, gives us a window into the nature of the matter that filled the universe when it was only a few microseconds old.

To push further back than that, to try to push back right to the very beginning, is essentially impossible, because the laws of physics are unknown to us under those conditions. But this time window, which begins at a few microseconds after the universe began, is essentially something we can understand with the current laws of physics as we understand them. And an area where we can actually make observations of the matter by, as I say, running back the clock through these collisions.

Kelly:  Why don’t you tell us a little bit about the most famous recent discovery, the Higgs boson.

Cormier: Yeah, the Higgs. The Higgs is an amazing discovery. As you said, it’s one of the few examples in physics where you built a facility and then, within the first year of operation, you’ve won the Nobel Prize with the three scientists to who it was awarded. That doesn’t happen very often, I’ll tell you, that thousands and thousands of people came together to build that machine, and it was a very single-minded effort in that sense. There was one thing that everybody was striving for, was to see if this particle existed. Because it was a missing link, essentially, in the theories that underpin our understanding of matter.

The theorists told us it had to be there. If it wasn’t there, then our understanding was really incomplete in some very fundamental way. So it was worth the – I don’t know, five to ten billion dollars that were spent to accomplish that result in the end, to build the biggest machine that has ever been built anywhere by human beings. And to operate it during the first year in a way that gave positive evidence for the existence of the Higgs boson.

What the Higgs boson does in the theories that describe it is rather complicated, but what it does is it gives everything mass. Without the Higgs boson, all the particles that we understand in the universe, all the atoms that we see around us, they would be massless. And it wouldn’t be much fun. Finding the Higgs was really important to having everything hang together. All the bits and pieces that make up the stuff around us, that it has any substance at all, is really due to the Higgs boson. It’s there, and in fact it’s amazingly simple once you see it. It stands out, it’s obvious, and was just out of reach for all these years until we built a machine big enough to find it.

Kelly:  It’s so interesting. As a souvenir there, I bought a coffee cup that has a simplified version of the formula. I mean, it makes it look very simple.

Cormier: Right, yeah, it’s—

Kelly:  And no, it’s not.

Cormier: It’s not simple, no.

Kelly:  I know it’s not.

Cormier: In fact, I think what you’re talking about is the QCD [quantum chromodynamics] Lagrangian, is what it’s called. In fact, you can write it down, but you can’t actually solve it in detail, because it’s a highly what a mathematician would call non-linear formula. There’s no way to actually solve it exactly. Now, we can solve it approximately in computers, which is what the theorists do these days, but it’s a beautiful formula. But basically too complex to really figure out with a pencil and a paper.

The people who did the experiments to discover the Higgs and so forth are really working in somewhat different fields from me. They collide protons and it makes all the difference in the world whether you collide two protons –– which are the smallest pieces of matter than you can isolate, ordinary matter that you can isolate, –– or the things that I do, which are to collide full lead nuclei and start with a large sort of macroscopic sample of matter. The people who studying the Higgs are looking for the next piece of the puzzle, which would be if there were more examples of the Higgs boson. Is it really only one, are there multiple Higgs bosons? Because those are variations of the theory, which would make the universe behave quite differently. This exploration of the so-called Higgs sector is looking for the kinds of physics that might be hiding in the neighborhood of the Higgs.

What this takes –– so as I said, we discovered the Higgs in one year –– what this takes now is many years’ investment, studying in much, much greater detail, the kind of events where the Higgs shows up. But looking to see what else is going on, maybe at a one part in a thousand or one part in a hundred thousand kind of level and digging deeper and deeper into the details. That’s good, old-fashioned, roll-up-your-sleeves kind of science, and that’s what’s going on now.

Kelly:  That’s what they’re doing.

Cormier: Yes.

Kelly: But what you’re doing—

Cormier: Yes. We collide lead nuclei, which is something that CERN does one month a year.
It’s actually possible to distinguish it by saying what the people who are colliding protons are doing are studying elementary particle physics, the physics of the elementary constituents of nature. Whereas, what the people who collide lead nuclei are studying is an extension of nuclear physics into this ultra-high energy regime. So one month a year—the accelerator runs for about seven, eight months a year—and so for 10, 12, 15% of the time, it does nuclear physics. For the rest of the time it does elementary particle physics.

The program of studying the nuclear physics is what I began my dissertation with here, which is to study the matter of the early universe. By colliding two lead nuclei at these fantastic energies, you create not a point-like object, which is what you get when you collide two protons, you create something that actually has a finite volume. A nucleus may not be very big, but compared to a proton, it’s gigantic. What we do is we take a sample of matter the size of a lead nucleus and heat it, as I said, to trillions and trillions of degrees, until the matter melts into a soup, which is very much like the early universe in the first few microseconds of its existence.

Then, our detectors help us study the properties of that matter and observe it as it expands and cools and turns back into ordinary matter. We can trace it from the instant of the collision, where the temperature goes from essentially zero all the way up to trillions and trillions of degrees in the collision, and then watch the collision come apart in our detectors as the matter cools back down. And can watch the transitions that it goes through, the same transitions that the early universe went through, where the early constituents of the universe was this soup of quarks and gluons at very, very high temperature, which expanded. The universe expanded through its first moments of existence, and as it expanded it cooled in the same way that our little mini-bangs expand and cool when we perform the collisions at the Large Hadron Collider.

So we can study how ordinary matter reappears. You start with these collisions, they create the matter of the early universe, and then study it as it reemerges as ordinary matter. What kind of matter is made? Do we make the protons and neutrons, for instance, that make up everything around us today appear in our collision? We start with matter, heat it to trillions of degrees where there are no protons and neutrons –– there are only quarks and gluons –– and then we watch it cool and expand. We watch the protons and neutrons emerge, again, from this hot soup, just the way they did from the early universe.

It is really an experimental probing of how the universe behaved in that first few microseconds, which we can then compare with the theories of the early universe. Now, these theories of the early universe, obviously, are very closely coupled to our other colleagues at the Large Hadron Collider, because this is a world that was full of elementary particles. You have to know how elementary particles behave. I shouldn’t have given the impression that we only work one month a year when we’re running the lead beams. We have to understand the collisions of the protons as well. It’s an important ingredient in understanding how those protons emerge when we study them with the lead collisions. It’s a full seven, eight months a year that we’re doing physics in Geneva.

Kelly:  That’s fascinating. So your team is actually collaborating with members of other teams that are dedicated to the particle physics. Do the particle physicists bring in members of your team, or is it a bilateral ––

Cormier: It is. All of the experiments – there are four experiments on the Large Hadron Collider. They are sited at locations where the beams intersect. The Large Hadron Collider has a circumference of about 21 kilometers, and as the beams go around that enormous ring, they collide at four different locations. At those locations there are these enormous experiments, and each of them studies the physics of these collisions from a slightly different perspective. That is, the detectors differ in the way they perform their observations, the kind of things that they measure. There’s a coherence in that the underlying physics is the same, but everybody’s looking at it in a slightly different way. There’s a very strong sort of cross-breeding between all the experiments and all the collaborators.

One of the things I do sort of in my spare time is I’m on the so-called ALICE thesis committee. We have, as I said, about 2,000 collaborators. Among those collaborators are hundreds of PhD students and those PhD students write their PhD theses. There may be as many as 50 PhD theses produced per year, just from the ALICE experiment. Then the students are invited to submit their thesis to be judged for the annual prize that goes out for the best thesis in ALICE. I’m one the guys who has to read all of those submitted theses. This year, we have twenty PhD theses, so that’ll keep me busy until about July.

Kelly:  Do you actually meet with the scientists, or just read the papers?

 Cormier: No, we know most of them. The young people are really the heart of the experiment, they do all the work. They are – you can’t miss them. They are there in the ALICE buildings and they are underfoot. They’re there and you know them well, and you know their work, you’ve known them for the three or four years that they’ve been doing it. They’re well-known to us.

It always comes down to a difficult choice. We have a committee, I think, of probably eight people this year who will look at these twenty or so theses that are submitted and try to judge the best one out of the bunch. It’s a difficult job. And again, every thesis is a little different. A PhD thesis asks a question, basically, and then the author of the thesis tries to convince you that he knows the answer, or she knows the answer. Everybody has a different take on it, and so it’s quite interesting to see how the young people are sort of continuing this kind of tradition of nuclear physics.

But now on such a mega scale that when I was a student, it would have been inconceivable that you could have a machine this big and you could actually make it work. Never mind make it work, but just imagine collaborating with a thousand people and getting anything done. Getting that paper written when there are a thousand authors is a task in itself.

Kelly:  Staggering. Goodness. On top of that, you’re dealing with, I’m sure, people from every nationality.

Cormier: Oh, yeah. In ALICE, there are, I think, represented about fifty to seventy separate national funding agencies, for example. It operates a little bit like a United Nations, a mini United Nations, to make all of those people focus on the same idea and cough up the money to support their share of it. The Department of Energy is one of the participants in that. They fund our work explicitly, but they’re also stakeholders and they contribute to running the experiment. It is a little bit like the United Nations, figuring out how much is your share and how much is my share.

Within that group of fifty to seventy or so national funding agencies, there are some that are dominant. They simply are the largest participants. They include the ones you would guess, probably: the United States and the major Western European countries and Russia and China, of course, and Japan. Basically all the countries that have very vibrant economies can sort of afford this kind of science. They tend to be leading groups in all of this. But every country, virtually every country is represented at some level, even if it’s only a single person. Azerbaijan is there, for instance. They have one student who is part of the collaboration. You’re right, every nationality is represented at some level, and some nationalities are more dominant, of course. As I said, they tend to be the ones that come from the countries with very strong economies and can kind of afford it.

It makes it – the common language in all of the scientific communications is English. But if you’re in the experiment, you’re hearing Italian and German and French spoken sort of simultaneously. It takes a little getting used to, actually, all that background noise in five different languages all at the same time. The scientific communication is in English and the papers are written in English. There was some debate, probably very early on, when CERN was first formed, whether it should be English or French, but English won out. I think official CERN communications are still in two languages. That is when they send out some political document, the top half is in English, the bottom half will be in French. But all of the real scientific discussion is in English.

Kelly:  Which is a big advantage for Americans.

Cormier: Oh, yeah, really. Because if I had to survive on my French, we’d be in trouble.

Kelly: I’m just curious about the number of women who might be involved in CERN work. If you don’t know precisely, what’s your impression?

Cormier: No, I don’t know precisely, but I’ll tell you there are some interesting trends that you can observe. For instance, women are a substantially larger fraction of the scientific community at CERN, if you look at the collaborators who come from France, for example. Same is true of Italy to some degree. Women in Italy tend to gravitate more toward physics than women in the United States do, for example. I’m trying to think. In the full U.S. team, not just Oak Ridge, but the full U.S. team consists of about –– well, it varies from year to year because the students come and go, but there may be 100 U.S. participants in this experiment. I’m going to guess that there are less than five or ten women in that group from the United States. Whereas, the fraction for the French group might also be 100 people, but they’d be closer to half women. So, it’s really a big ––

Kelly: That’s astounding.

Cormier: Yeah, it is.

Kelly:  So Marie Curie lives on.

Cormier: Yeah, I think, in fact, there’s an influence of exactly that. That’s right.

Kelly: What do you think the future holds?

Cormier: This is a big topic of discussion, of course, because the Large Hadron Collider took approximately twenty years to realize. The planning for it started twenty years ago. The building of these big experiments takes ten to fifteen years, even once you know what you’re going to build. You need to get the funding in place and so on and so forth. It’s a twenty year commitment to getting this machine running.

The planning for what comes next started quite some time ago already. There are a number of options on the table. It doesn’t cost a whole lot of money to explore options, but once you select one, then it gets expensive. There are options. There is the so-called Future Circular Collider. The Large Hadron Collider, as I said, is a circle about 21 kilometers in circumference. The Future Circular Collider would be about ten times bigger than that. It would cover a substantial fraction of the western end of Switzerland and that region of France, and would have an energy that would be ten times higher than the current energy. 

There are other ideas, however. There’s the so-called Compact Linear Collider, which is where you basically give up on the idea of running beams in a circle, so that you can reuse them. But rather make accelerators that are linear, straight lines, and they simply just shoot particles at each other. You can have a machine that maybe is 100 kilometers long and the beams come at each like the bullets from two guns traveling in opposite directions and you have collisions like that.

Each of these approaches has their own team pushing for them. R&D is going on in both kinds of futures. But again, these are facilities that are so big –– we’re talking now ten times the scale of what has just been accomplished –– that this really now takes complete involvement of the whole world. Whereas the U.S. participation in the building of the Large Hadron Collider was at the level of some percent, probably, of the total budget for the thing. Although there were very significant technical contributions from all the national laboratories, for example. It would take from the major economies of the world far more substantial investments to realize now a facility which is ten times the size of the one that we have now.

All the usual problems then have to be worked out. Where are you going to build it, first? The Japanese would like to have it in Japan, for example, and U.S. senators would like to see it near Chicago. Those discussions will go on forever, and at the end of the day, the country that comes up with the most money probably has the most to say about where the thing gets built. The future is – because the lead times are so long on these projects, people are already thinking about what will happen now ten years from now, twenty years from now.

I think there’s one thing I would say just to sort of frame this kind of work. It’s a little bit different from a lot of the science that your typical high school student may think of when he or she thinks of science. They think of the chemistry laboratory, behind the little door and so on and so forth. This is truly Big Science. This is science of the scale of the Apollo lunar landings, for instance, which was undertaken, of course, entirely by the United States. Now science of this size is of such a scope that it really needs to be undertaken by the whole world together.

That’s an important part of this, I think, and that attracts some people to it. It pushes some people away, because they just see it as so much chaos. There are long periods of chaos, there’s no doubt about it. But in the end, when it all comes together and works, it’s really quite impressive that you can really get that many people moving in the same direction. It’s an exercise, really, in sociology as well as science, which is kind of fun.

Kelly:  People talk about can we have another Manhattan Project, and World War II was such a galvanizing force ––

Cormier: Right, exactly.

Kelly: Right, and you had all the prima donna scientists that [J. Robert] Oppenheimer had to corral. Some of them were a little wayward, but most of them were very focused.

Cormier: Right.

Kelly:  But that’s very hard to recreate.

Cormier: Right. That’s exactly right, and there’s an interesting outgrowth of that. What I call Big Science actually begins – well, the first example of that is the Manhattan Project. Because prior to that, governments around the world did not invest in science at all. You had private foundations or universities or whatever investing in science, and that really limited the scope of what you could do. But after the Manhattan Project, it became clear that the way to really get things done is to put the backing of major governments behind certain scientific initiatives. Then you can see what –– you can land on the moon, you can build the Large Hadron Collider. 

That really begins with the Manhattan Project. This whole idea of government investing in science really came out of the Manhattan Project.

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