Kerven Louis
Physics 102
Anti-Matter

Antimatter is a material composed of antiparticles, they have the same mass as any normal particles that makes matter but have opposite charge and other particle properties such as lepton and baryon number ( Kragh 2002). When normal particles and antiparticles encounter each other it leads to the annihilation of both and gives rise to certain high-energy photons or gamma rays, neutrinos, and lower-mass particle–antiparticle pairs. Setting aside the mass of any product neutrinos, which represent released energy which generally continues to be unavailable, the end result of annihilation is a release of energy available to do work, proportional to the total matter and antimatter mass, in accord with the mass-energy equivalence equation, E=mc2. Antiparticles have been found in cosmic rays, and are also produced in particle accelerators also known as atom smashers. An antiparticle never lasts for very long, because shortly after it forms, it encounters one of its equivalent matter particles, and both are annihilated, yielding pure energy.( Thompson 1997)

Artificially produced antimatter can have some practical applications, especially in medical science, where it is involved in the operation of positron emission tomography scanning equipment. Antimatter has been suggested as a possible propellant for spacecraft, a source of energy for public consumption, and as material for a doomsday bomb that would vaporize the earth. (G. Weidenspointner et al. 2008)
The discovery of antimatter is one of the most important scientific events of the twentieth century. Big discoveries in science are a result of chance most of the time . However, the existence of antimatter was predicted before anybody had actually been able to observe it in the real world. In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behavior of an electron moving at a relativistic speed. But the equation which won Dirac the Nobel prize in 1933 posed a problem like just as the equation x2=4 can have two possible solutions (x=2 or x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. But classical physics and common sense dictated that the energy of a particle must always be a positive number.( Shen, Y. 1983)
Dirac interpreted the equation to mean that for every particle there is , it exists another corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron there should be an "antielectron", for example, identical in every way but with a positive electric charge. The insight opened the possibility of entire galaxies and universes made of antimatter. But when matter and antimatter come into contact, they annihilate and disappear in a flash of energy. The big bang should have created equal amounts of matter and antimatter but it didn’t. This raise the question of why is there far more matter than antimatter in the universe( Shen, Y. 1983) Four years after Dirac's formula, in 1932, the American physicist Carl Anderson, from the California Institute of Technology, observed a positron for the first time and succeeded in photographing it. This discovery was to a certain extent a result of chance. Anderson was investigating the behavior of cosmic rays, particles and radiation that reach us from space. He was observing their motion through a device called cloud chamber that makes it possible to observe the trajectory of the particles constituting cosmic rays. He had successfully identified neutrons and electrons when he also discovered certain particles that behaved in the same way as electrons, but moved in the opposite direction. It was the first irrefutable evidence of the existence of positive electrons or positrons. The discovery earned him the Nobel Prize in 1936.From then on the search for the remaining antimatter particles started. The negative proton, or antiproton, was found first. But this time it was not a question of chance, scientists had to design complex experiments to produce it. (G. Weidenspointner et al. 2008)
The first production of antiprotons was accomplished by the physicists Emilio Gino Segro and Owen Chamberlain in 1955 at the University of California Berkeley bombarding a copper shield with high energy protons. The experiment was carried out in the particle accelerator built by Ernest Lawrence at the Lawrence Berkeley National Laboratory. It was the Bevatron, a ring capable of accelerating protons to an energy of 6.2 GeV . Segro and Owen's discovery earned them the Nobel Prize in 1959. Nowadays, the largest particle accelerator in the world the Tevatron at the Fermilab laboratories in Chicago is capable of generating energies of up to 1.8 TeV by colliding protons and antiprotons (Amoretti et al. 2002).
Only a year later, in 1956, B. Cork, O. Piccione, W. Wenzel and G. Lambertson, a second group of Berkeley researchers, announced the discovery of a third antiparticle: the antineutron. Once the existence of these three antiparticles (antielectron, antiproton and antineutron) had been proven, the efforts shifted to the production of the first antimatter atomic nuclei. The goal was fulfilled in 1965 with the observation of the antideuteron, the nucleus of the atom of antideuterium, consisting of an antiproton and an antineutron. Two teams of researchers succeeded in producing it at the same time: Leon Lederman's team at the Brookhaven National Lab New York and Antonino Zichichi's team at CERN. (Amoretti et al. 2002).

The following big goal was the production of whole atoms of antimatter, instead of just nuclei. The chosen atom was hydrogen, because it was the simplest element with just one electron and one proton in its structure. (Amoretti et al. 2002). Hydrogen is also one of the best studied elements, and constitutes three-fourths of our universe and the basis for our scientific knowledge of it. In 1995, 30 years after the production of the first nuclei, a team of researchers from Germany and Italy finally announced the production of the first antihydrogen atoms. The experiment was possible thanks to a new machine: the Low Energy Antiproton Ring or LEAR. This device decelerated the antiprotons produced in the particle accelerator and stored them in a ring, so that scientists could study them at their leisure and, for instance, combine them with positrons to produce stable atoms. A year later the laboratory Fermilab announced a similar production of antihydrogen atoms as well. (B. Steigerwald 06)
The main reason is its scientific research antimatter it’s to allows us to learn more about our universe. The ALPHA collaboration, for example, wants to study if matter and antimatter are exactly symmetrical. The laws of physics offer certain predictions in this respect, but experimentation could prove them wrong. It is through this process of observation, prediction and testing that science advances. (G. Weidenspointner et al. 2008)
The study of antimatter is also appealing for other reasons. The annihilation of matter and antimatter is a process that generates surprising amounts of energy, very superior to what can be obtained through chemical or nuclear processes Only half a gram of antimatter in contact with half a gram of matter would liberate the energy of a 20 kiloton nuclear bomb, that is, the energy of a nuclear bomb like Hiroshima. Since there is not such a thing as a mine of antimatter in the universe, if we want to use antimatter, we have to produce it first. The problem is that the quantity of energy necessary to produce antimatter is very superior to the amount of energy obtained from the annihilation processes.To this one may also add the difficulty in storing antimatter particles, since nowadays we don't have the technology to store even a trillionth of a gram of positrons. (G. Weidenspointner et al. 2008)

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