Recent results of a joint experiment conducted by 460 physicists from 57 research institutions in 12 countries strongly indicate that the scientists have succeeded in reproducing matter as it first appeared in the universe, matter called the quark-gluon plasma. The experiment, called PHENIX and conducted at the Brookhaven National Laboratory on Long Island, New York, has brought together physicists from Brazil, China, France, Germany, Hungary, India, Israel, Japan, South Korea, Russia, Sweden and the United States. The Israeli team is led by Prof. Itzhak Tserruya, head of the Weizmann Institute’s Particle Physics Department. Tserruya and his colleagues have designed and built unique particle detectors that are a central part of PHENIX's detecting system.
In the first millionth of a second after the Big Bang, the atoms of different elements as we know them today did not yet exist. The main components of atoms, protons and neutrons, had not yet been “born” either. The jets of blazing matter that dispersed in all directions in the first few fractions of a second in the existence of the universe contained a mixture of free quarks and gluons, called the quark-gluon plasma. Later on, when the universe cooled down a bit and became less dense, the quarks and gluons got “organized” into various combinations that created more complex particles, such as the protons and neutrons. Since then, in fact, quarks or gluons have not existed as free particles in the universe.
Scientists studying the unique physical properties of the quark-gluon plasma have been trying to recreate this primordial matter using an accelerator, called RHIC, built especially for this purpose at the Brookhaven National Laboratory. This accelerator creates two beams of gold ions and accelerates them one towards the other, causing a head-on collision. The power of the collisions (about 40 trillion electron volts, also termed 40 tera electron volts) turns part of the beams’ kinetic energy into heat, while the other part of the energy turns into various particles (a process described by Einstein’s well-known equation E=mc2). The first stage in the creation of these new particles, like the first stage of the creation of matter in the Big Bang, is assumed to be the stage of the quark-gluon plasma.
One of the ways to identify the quark-gluon plasma is to observe the behavior of particles entering the plasma. When a single quark propagates through regular matter (containing protons and neutrons), it emits radiation that slows down its progress somewhat. In contrast, when it enters a very dense medium like quark-gluon plasma, it will slow down much more. That’s precisely the phenomenon that has recently been observed and analyzed in the PHENIX experiment. According to the physicists taking part in the experiment, these findings could indicate that they have succeeded in creating the quark-gluon plasma.
The detectors designed and built by Prof. Tserruya are capable of providing three-dimensional information on the precise location of the particles ejected from the collision area. These particles' direction, together with their energy and identity, help distinguish the matter's properties in the collision area. Apart from Prof. Tserruya, the Weizmann team that designed and built the detectors included Prof. Zeev Fraenkel, Dr. Ilia Ravinovich, postdoctoral fellow Dr. Wei Xie and graduate students Alexandre Kozlov, Alexander Milov and Alexander Cherlin.
Prof. Tserruya's research is supported by Nella and Leon Benoziyo Center for High Energy Physics.
Prof. Tserruya is the incumbent of the Samuel Sebba Professorial Chair of Pure and Applied Physics.
The Weizmann Institute of Science, in Rehovot, Israel, is one of the world’s foremost centers of scientific research and graduate study. Its 2,500 scientists, students, technicians, and engineers pursue basic research in the quest for knowledge and the enhancement of humanity. New ways of fighting disease and hunger, protecting the environment, and harnessing alternative sources of energy are high priorities at Weizmann.