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Elementary Particles

Studying Elementary Particles

antihydrogen, antiparticles, antiprotons, positrons, electric fields

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>  Particle Accelerators and Colliders

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>  Particle Traps

Scientists use particle traps to study particles that are more stable and have less energy than particles studied in accelerators and colliders. Magnetic and electric fields can be used to trap charged particles. The fields control the movement of the particle, keeping it confined to a small area. Neutral particles, such as atoms, can also be trapped, but that task is much more difficult. Lasers, beams of coherent light, are often used to trap neutral particles. Light carries energy, and when light strikes an object, it exerts a small force on the object. Shining lasers on atoms or other neutral particles causes the particles to gradually slow down and be trapped.

The rules of quantum theory prevent any particle trap from being perfect. A perfect trap would enable a physicist to precisely determine a particle’s position and speed. A rule called the uncertainty principle states that a particle’s location and speed cannot be precisely measured at the same time. Increasing the precision in one measurement increases the uncertainty in the other. If a particle trap was infinitely small, the location of the particle would be known precisely, but this would make measurement of the particle’s speed infinitely uncertain: The scientist would not be able to determine anything about the particle’s speed. Likewise, if the particle trap slowed the particle to a complete rest, its speed would be known precisely, which would make the particle’s location infinitely uncertain: The scientist would not be able to determine anything about position, or whether the particle was even in the trap.

Scientists use particle traps to compare the properties of particles and antiparticles. Scientists are also trying to create antihydrogen using particle traps. Antiparticles, such as antiprotons and positrons, usually exist for just a brief time before they combine with their counterpart particles in ordinary matter and are annihilated. A particle trap, however, can confine an antiproton without letting it contact its ordinary matter counterpart, the proton. Positrons can be confined in a similar manner. Researchers are currently using particle traps to bring positrons close enough to antiprotons so these particles can bind and make antihydrogen, just as electrons and protons make hydrogen.

Particle Detectors

Before the development of particle physics, scientists had a difficult time explaining the behavior of light. Light often behaves like a wave, such as a wave of sound or a wave on the surface of water. Other times, however, light behaves more like a beam of particles. To explain this behavior, Albert Einstein proposed in 1905 that light came in little packets, or particles, of energy. He was awarded the 1921 Nobel Prize in physics for his explanation. In 1926 scientists named these particles of light photons.

Article key phrases:

antihydrogen, antiparticles, antiprotons, positrons, electric fields, Albert Einstein, atoms, physicist, electrons, accelerators, Nobel, scientist, explanation, difficult time, task, measurement, scientists, precision, movement, object, speed, Researchers, energy, position, times, time, location

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