Argonne National Laboratory

Kawtar Hafidi

By Louise LernerFebruary 5, 2012

Kawtar Hafidi is an experimental physicist at Argonne National Laboratory, studying how fundamental particles, namely quarks and gluons, form nucleons and nuclei. She led the Women in Science and Technology (WIST) program at Argonne.

How did you get interested in science?
Well, I came from a family where both my parents didn't graduate from high school. At that time in Morocco it was not uncommon; many people would reach the 12th grade and leave, because under the French occupation, we didn't have universities in Morocco—you had to leave the country to go to college. So only a few people were highly educated.

However, I did well at school, and my dad was proud of that. He was not rich, but he insisted on paying for private school. And this, I think, gave me a head start, because it's much more serious. My father invested in that. It was hard for him, but he did; for him, education was very important.

And as for me, I loved school. I always wanted to stay longer. I used to love writing, in both French and Arabic, and I was also good at math. I used to spend my summer doing complicated math problems. One day at school the teacher asked me why I didn't do my homework. I said, "I don't want to." He asked me why, and I said, "Because I'm afraid they will be finished!" [laughs] We didn't have many books at that time, so I'd find one book and do just one problem a day, like eating a cake, you know—you don't want to be finished.

Then what happened?
In Morocco in the ninth grade you have to decide if you'll do science or literature. And there's no going back. I wanted to do literature, but my dad was against it. He said, "What will you do with literature? It's not useful to the country. Since you are good at everything, you should do science." So he convinced me, and I went ahead with science, because I thought I could help my country this way. So I started mathematics and physics in university.

Did you like it?
I did. But I was also conflicted. Because science, it's rigorous; however, except for tutoring, you don't feel like a direct help to society and people. Especially when you are doing object-oriented science such as mathematics and physics, as opposed to people-oriented sciences, such as biology and medicine. And this always made me angry. My happiness is when I make others happy. And although in science I have grad students and colleagues, it's not the same. It's not easy. Maybe I did the Women in Science and Technology program at Argonne because I could do that for people, and it makes me so happy.

Scientific accomplishments of course make you happy and proud, but it's a personal achievement. You do your research, get results, then you go present it in a conference—it's your own ego. However, when you go to work with people and try to solve their problems, maybe nobody knows what you did, only the person that you helped. But that's great.

What are you working on right now?
I am a member of the medium-energy physics group, studying nuclear physics. Not reactors, but the fundamental science of nuclear forces.

So you have the nucleus, which is very tiny. You want to study it. How do you do it? You need a camera to take a picture. The camera is the accelerator. We accelerate particles, and the more you accelerate them, the more high-resolution photos you can take. Scientists started with particles at lower energy, which just gives you a nucleus as a blob. You can't see much. Increase the energy and you can start to see protons.

Higher energy gives us a better look inside the proton. Inside, there are quarks, though we can't see them directly. The lightest, and most famous, quarks are the up quark and down quark. There are six quarks in all: up, down, strange, charm, top and bottom. And they each have an electric charge. The proton itself has a +1 charge; the quarks have a fractional electric charge.

But in addition to the electric charge, there is another charge. This is the color charge. Red, green, blue, and anti-red, anti-green, anti-blue. In nature, however, all you see is "colorless" charges; that is, they add up to color charge zero. If you have three colors together—and they are not really true colors, that's just a name—all of the quarks have to have net color charge zero.

How do you study quarks?
You need an electron from a high-energy accelerator. The electron hits the quark, and you try to take a quark out using that energy. But the quarks have forces acting on them. See, when they are near each other, they move freely. It's like—say you have two horses tied to each other with a long string. They can move without noticing they're attached. The only time they notice is when they want to be far apart. The quarks are the same. Between them they have gluons, like springs, like glue between them. When you try to take one quark out, the string between the quarks will stretch, stretch, stretch—but with high enough energy you can break that string.

What happens? At the end of the string, all of a sudden, the quark will have another anti-quark with him. And the two other quarks will have another quark with them. The quarks are very social animals. They don't like to be by themselves. They are always in pairs or threes. And that's why we need the strong force. Because the quarks are confined to each other, and it takes a lot of force to break that.

What kind of experiments do you run?
The theory that describes this phenomenon is called quantum chromodynamics, or QCD. We need to do measurements to guide the theory of how quarks form protons and nuclei. QCD has a lot of predictions, and I study specific aspects of that.

I do my experiments at a six gigaelectron-volt accelerator at Jefferson Lab. For example, one of the QCD predictions tells you that in specific conditions, you can create particles that will traverse the medium freely. Those particles will be invisible to the medium. It's like if I shot a particle at the wall, and it went straight through the wall without interacting with it. This phenomenon is called color transparency, and the experiment I did is the first proof of this concept at low energy.

We do several experiments like that. It's what is called fundamental research. People ask you, "What's the implication? What's the use?" When we start looking at quantum mechanics, it's abstract. But if we didn't understand quantum mechanics, we would not be able to understand chemistry. The same is certainly true for quantum chromodynamics. When you understand things, many applications naturally come up. It's not enough to have an engineering formula, to apply; we need to get the formula, to understand it. We need all of it.

What's the best part about your work?
There are many parts that are very fulfilling and rewarding. I like the process of research, from reading articles, discussions with my colleagues—suddenly, you get the idea! Then you have to do the simulations to see if the experiment is possible. Later you have to defend your idea in front of peers and last get beam time and build detectors to realize it.

I also love my graduate students. I tell my students and postdocs, we are a family. I love them. I am so proud of them. Seeing them develop and grow is very rewarding.

I also know it's not just work, because it doesn't stop. I go home, but I don't stop thinking about science. Sometimes I wake up at 3 a.m. and can't sleep and have to do my work. In the shower I'll think of something and have to go write it down. So it's non-stop. It's a way of life. It's really not a job.

Did you notice a difference between women in science in the U.S. vs. other countries?
Well, I went to undergrad in Morocco, but then went to Paris for graduate school. Let's start with Morocco. The number of women scientists is larger than the U.S. in proportion—they have a lot of professors. Of course, Morocco doesn't have that many universities, but it still stands.

However, research in Morocco is not that demanding. We have a few purely research centers, but most of the research is done at universities, and I think women want to be professors because it's flexible. They teach maybe four hours a week, and then nobody asks them where they are. They demand less time and work from scientists. That is different in the U.S.

So maybe that's the reason Morocco has more women scientists. If Morocco became very demanding like the U.S.—you have to work so many hours, you have to be away from your family, you have to make choices whether or not to have children at a specific time—I think Morocco would have the same hard time having women in those positions. So I think that's the major difference.

In France, I think the numbers are a little bit better than the U.S. In France they take care of a lot of sociology. When women have children, they can get 16 weeks for the first and second child and 26 weeks for the third with pay and up to two years without pay. Even vacation: men and women get two months' paid vacation. Yeah, you don't know what to do with all of your vacation. So yes, the social part is very important.

What's the big challenge in your field?
Well, in the field of nuclear physics, we still need to understand a lot. We have quarks, which are the smallest particles—there are no particles inside them, as far as we know. From those quarks, which we can't see as individuals in nature, how do they form the matter that we see? How do we form protons and neutrons? And more importantly, how do we form nuclei? What's the lifetime of a quark? Does it vary according to the type of quark?

We cannot study quarks alone; they are always inside something, which makes it very complicated.

What do you do in your free time?

I play soccer. Actually, when I was around 16 and 17, I was almost a professional soccer player. At that time they started building the national Moroccan women's soccer team. I didn't get a chance to play a lot with them, but I was part of them. But when you're studying, you know, you just don't have enough time. Now I play tennis, ping-pong, pool, and more importantly, fishing is my thing. Anytime there's good weather, I go. And I fish at night, to catch the big fish. In this area, flathead catfish, bass, walleye, big carp. I am also preparing my black belt in mixed martial arts.

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