John D. Reid Research Interests Post Doctoral Research

Heavy Ion Collision (The moving nucleus is Lorentz Contracted.)

Heavy Ion Physics
Heavy Ion physics is a field where relatively large atoms are collided. Gold atoms and lead atoms are commonly used. Atoms have equal numbers of electrons (negative charge) and protons (positive charge). This makes them neutral. In heavy ion collisions, atoms are stripped of most of their electrons, making them ions, and then accelerated forming a beam of ions, which are aimed at target atoms, or another beam of ions. Since the atoms are made up of protons and neutrons in the nuclei, the resulting collision is a complicated tangle of hundreds of particles. Nevertheless, much can be learned about the structure of nuclei from the results of such collisions. In addition to learning about the structure of nuclei, many heavy ion experiments are designed to study the state of matter under such hot and dense conditions resulting from a relatively large amount of energy existing in such a small region of space. For example, it is thought that the conditions that exists in these collisions might be similiar to very early times in the origins of the universe, shortly after the Big Bang, when matter was so dense and hot that protons and neutrons could not exist. Instead their constitutents, quarks, were could move freely. Thus the nature of matter changes at high temperature and density just as ice changes phase when temperature and density changes. These heavy ion experiments are, in some ways, analagous to smashing two ice cubes together and looking for evidence of water.

Brookhaven Experiment E864 - The Search for Strange Matter

This experiment collided gold ions with heavy targets such as lead. The result of such a collision, at the energies we used, is a hot dense system of nucleons (protons and neutrons). If the system is hot and dense enough, it is thought that particles called strangelets might be produced. Most ordinary matter consists of two types of quarks called, the up quark and the down quark. Up and down quarks are what make up protons and neutrons in ordinary matter. Particles consisting of up and down quarks seem to be the most stable particles. Some theories predict that, under certain conditions, a heavier quark called a strange quark, could combine with up and down quarks to form stable matter. Some theories predict that strange matter may exist on astronomical scales inside certain types of neutron stars. This experiment was designed to look for evidence of strange matter produced in heavy ion collisions between gold and lead. No evidence was found in this experiment. Such is the nature of science. The experiment was able to state, precisely, a range of conditions where strange matter was not seen. This is useful information, which can help direct theoretical preditions for the existence of strange matter and help direct other experiments looking for strange matter.

E864 Home Page - Post Doctoral Research 1993-1997
Brrookhaven National Laboratory, Long Island, NY
Experiment E864 - Search for Strange Matter.
E864 Documents - Official Documents Page for Brookhave Experiment E864 - Search for Strange Matter.

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