The first collisions of particles that will allow scientists to study matter as it existed just after the Big Bang were observed today with the help of unique particle detectors designed and built at the Weizmann Institute of Science in Israel.
The collisions marked the launch of the largest experiment of its type at the Brookhaven National Laboratory in Long Island, intended to simulate the first stage in the creation of matter in the universe. This experiment, called PHENIX, involves some 450 scientists from 11 national groups, including the Israeli team headed by Prof. Itzhak Tserruya of the Weizmann Institute’s Particle Physics Department.
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 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” in 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 particle accelerators. In an experiment called CERES, conducted at the European Laboratory for Particle Physics (CERN) near Geneva, an international team including Weizmann Institute scientists came close to that goal. But in order to be certain that the goal has indeed been achieved and to maintain the quark-gluon plasma sufficiently long in order to study its properties, a special 3.8 kilometer circumference Relativistic Heavy Ion Collider (RHIC) was built at the Department of Energy’s Brookhaven National Laboratory.
RHIC creates two beams of gold ions, accelerates them almost to the speed of light and
causes them to collide. The power of the collisions, about 40 trillion (40 million times one million) 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 in Einstein’s famous equation E=mc2. The first stage in the creation of new particles, just as in the first stage of the creation of matter in the Big Bang, is assumed to be the stage of the quark-gluon plasma.
The 20 Weizmann detectors designed and built by Prof. Tserruya are crucial elements of the PHENIX detection system, intended to definitively identify the quark-gluon plasma. They are capable of providing three-dimensional information of the precise location of the particles ejected from the area of the collision. The direction of the particles’ motion, their energy and their identity will allow scientists to study the state of matter in the area of the collision. The PHENIX experiment is scheduled to run several years.
Among the distinguishing features of the Weizmann Institute detectors is the fact that they are both lightweight and strong, a rare combination of properties. Also, they contain several unique elements, such as extremely complex printed circuits. The Institute scientists were able to find only one company in the world, located in Italy, that was able to manufacture the circuits matching their specifications.
Apart from Prof. Tserruya, the team that designed and built the detectors included Prof. Zeev Fraenkel, Dr. Ilia Ravinovich, postdoctoral fellow Dr. Wei Xie and graduate students Alexander Gnaenski, Alexander Milov and Alexander Cherlin, all from the Weizmann Institute’s Particle Physics Department.
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.
