Massless fermions are particles that have zero rest mass and follow the laws of quantum mechanics. They are fundamental particles that make up the building blocks of matter, and are classified as fermions because they have half-integer spin.
Massless fermions differ from other particles in that they have no rest mass, meaning they always travel at the speed of light. They also have unique properties such as chirality, which describes their left- or right-handedness, and helicity, which describes their direction of spin.
Yes, massless fermions do exist in reality. The most well-known example is the photon, which is the carrier particle of electromagnetic force and has zero rest mass. Other examples include the neutrino and the gluon.
The existence of massless fermions plays a crucial role in many areas of physics, such as particle physics, cosmology, and condensed matter physics. They also help to explain fundamental interactions between particles and play a role in the Standard Model of particle physics.
Yes, massless fermions can have a measurable effect on the world around us. For example, the photon is responsible for the transmission of light and other forms of electromagnetic radiation, and the neutrino has been detected in various experiments studying nuclear reactions and cosmic rays.