Julia Velkovska’s Wayward Particles Collide with Physicists’ Expectations

In 1989 a young couple of ambitious and promising Bulgarian physicists decided that the boundaries of Bulgaria are too narrow for their dreams of big science. They passed examination and won assistant professor’s positions in the state university of New York in Stony Brook.

The first years of self-assertion were very hard but the successes of the young scientists won deserved recognition. In 1997 they became doctors of philosophy. What is more, they had the rare chance to participate in something entirely new in world science. They took part in the design and construction of the largest heavy ion accelerator in the world RHIC, which the Brookhaven National Laboratory developed in 2000. Gold nuclei were accelerated to a speed near the speed of light and brought into collision. This collision generated a temperature close to that of the early Universe. The purpose was to study the so-called quark-gluon plasma formed in the first microsecond after the explosion, which created the Universe. And today, more than 3 years after the start of the experiments, there are convincing proofs that such quark-gluon plasma was created. Analyzing data from the experiment called Phoenix, Julia made a shocking, unsuspected discovery regarding the baryon particles. Science magazine (vol. 298, No 5594, p.718, 25 October, 2002) published it in its news section under the heading: “Wayward Particles Collide With Physicists’ Expectations”. The Bulgarian physicist made a boom in world science. She was showered with invitations to report before the societies of the most famous physicists worldwide. The days of the young woman were divided between her teaching as professor in the Vanderbilt University in Nashville, Tennessee, her work in the Phoenix experiment, the numerous reports which took her to different points on the planet, and her big family – her husband Momchil, also a physicist, and their three sons.

Julia, I know you finished the English Language School in Burgas and the Music School as a private student. Where did your interest in Physics come from?
I came to like this science in the 7th grade. My Physics teacher was very good. I graduated in Physics from Sofia University, then I became a post-graduate student. I married a physicist, also a post-graduate student. At some point we felt that if we wanted to develop we had to seek a wider field for self-fulfillment. Thus we and our 10-month-old baby came to Stony Brook. This is a comparatively young university, only 40 years old, but it ranks second among all US state universities. It has produced one Nobel Prize winner. The faculties of Physics and Medicine are the most potent. Many world-known scientists teach there.

It must have been very hard in the beginning?
We did fight a great battle. We had two years to show who we are, what we can and whether we have prospects for development. For two years, while our son Stoicho was in the day care of a babysitter, Momchil and I read lectures at the university, we studied, we had weekly tests and long daily homeworks. At the end of this trial period we passed examination in everything, which was decisive – we would either stay or pack and leave. But we made it.

There is something symbolic in the fact that on June 1, in Gemini, your twins Ivan and Pavel were born. Not everybody has the chance to have twins. I think this is a good sign of Fate.

I suppose at that time your work fell into the background?
Far from it. Ten days after delivery I was back in the laboratory. There is no maternity leave for research fellows there. Nobody wants to know about your family concerns and what is more, female scientists with children (to say nothing of three) are not looked upon favorably. The Americans either make a career until 40 and then give birth to their children, or devote themselves to the family and children and forget about everything else. I don’t think in Stony Brook University there was another case as ours.

Was it at that time that you started working in the experiment, recreating, to put it in the simplest terms, the first moment of the existence of the Universe?
My husband was engaged in the theoretical part, and I worked in the laboratory on one of the two large detectors which were to record the experiment results.

Are you two in competition as scientists?
No, we are a team to a yoke, both in science and at home. We don’t compete. At that time Momchil could have gone far ahead of me but he consciously slowed down his work to pull me, to go side by side. At one time he took over all the work at home to let me catch up. Later I pulled him by my side. The Vanderbilt Faculty of Physics was very eager to hire me. I agreed to go there on the condition that they provide a research professor position for Momchil. So, for a year now we have been in this university. It is a great success for us. Many couples of physicists have suffered because they could not get jobs at the same place. It is incredible, but the stronger the people are the harder it is for them. We are a lucky exception.

Vanderbilt is a private university, among the best in the South. I teach and I find this very interesting, it keeps me in good shape. I have to know the answers to many questions and be able to explain them to the students well. Momchil shifted from theoretical to experimental physics, and now to biophysics. He has exceptional knowledge in many fields, which enables him to work different things. He is not teaching now. He is only doing research.

Your work is related to a very sophisticated subject. Can you put in simple words what it is about?
Since time immemorial people have wondered “What is the world around us made of? Which are the fundamental (indivisible) particles of matter? What forces bind them?” The concept of element exists since the time of Empedocles (5th c. BC). He thought the world was made up of earth, air, fire and water. Half a century later Democritus introduced the term “atom” and the idea that there exists a smallest indivisible particle of matter. Ever since humanity has been looking for these particles. We have gone a long way – from Mendeleyev’s table to the structure of the nucleus. Today we know that atoms have a nucleus and an electron shell. The nucleus consists of protons and neutrons, and the protons and neutrons consist of quarks and gluons. Are these the smallest particles? Shall we discover new, even smaller particles?

It seems simple at first sight but sometimes these discoveries take centuries, don’t they?
The present-day idea is that the smallest particles of matter are the quarks, the leptons (an electron plus two similar but much heavier particles) and the particles that make their interaction (photons, gluons, W- and Z-bosons). Are we sure we have not missed any? Maybe tomorrow we’ll discover something even smaller. Unlike ancient thinkers, modern scientists do not rely mainly on their imagination but put every thesis to the test. Theories that cannot be confirmed experimentally are considered unscientific.

Today we have a very successful theory of elementary particles: the Standard Model. The only undiscovered one yet is the X-boson, a mysterious particle that makes the rest massive. Another unsolved mystery is the fact that the quarks and the gluons have never been observed in a free state. Even if you succeed to knock out a “naked” quark from the nucleus by hitting it very strongly, with say a fast-moving electron, it will quickly “dress” in quarks which spring from the vacuum, just so as our knocked out quark would not be lonely. The mystery of the bound quarks – this is the subject of high-energy nuclear physics.