An Introduction to Antiparticles and Their Properties

One possible way to explain the concept of antiparticle using a daily life analogy is to compare it to a mirror image. Imagine that you are looking at yourself in a mirror. You see a person who looks exactly like you, but with some differences. For example, if you raise your right hand, your mirror image raises its left hand. If you wear a watch on your left wrist, your mirror image wears it on the right wrist. If you have a mole on your cheek, your mirror image has it on the opposite cheek. These differences are analogous to the opposite physical charges of particles and antiparticles. For example, the antiparticle of the electron is the positron, which has the same mass but opposite electric charge.

However, unlike a mirror image, an antiparticle can interact with its corresponding particle and annihilate each other, producing photons (particles of light). This is similar to what happens when matter and antimatter come into contact. For example, when an electron and a positron collide, they disappear and produce two gamma rays. This process is exploited in positron emission tomography (PET), a medical imaging technique that uses radioactive substances to create images of the body.

Another difference between a mirror image and an antiparticle is that some particles are their own antiparticles, meaning that they do not have any opposite physical charges. For example, the photon is its own antiparticle. This means that a photon does not have a mirror image that is different from itself.

The concept of antiparticle was first predicted by Paul Dirac, a British physicist who developed a theory that combined quantum mechanics and special relativity. He realized that his equation allowed for the existence of particles with negative energy, which he interpreted as antiparticles with positive energy. Later, Carl Anderson discovered the positron in cosmic-ray collisions using a cloud chamber, a device that can detect charged particles by the trails they leave in a gas. This was the first experimental confirmation of Dirac's theory and the existence of antiparticles..