During 1960’s, neutrinos had only two kinds i.e. (,) neutrino and antineutrinos which had opposite helicity. Over the years, three different flavours have been discovered i.e. e, which carry the signature of the particle with which these were emitted. Going by the analogy, one can ask a layman question, whether photons do also come with different flavors?
Ravinder,
I can only attempt a layperson answer... The three flavors, or generations, of matter (fermions) in the standard model of particle physics are distinguished by their increasing rest mass. Among these generations, the types of particles' interactions are identical. Please see http://en.wikipedia.org/wiki/Standard_Model and http://en.wikipedia.org/wiki/Generation_(particle_physics). The fermion particles are divided into quark and lepton types: the quarks are subdivided by charge into those with electrical charge of 2/3 (up-type) and -1/3 (down-type). The leptons are subdivided by those with a charge of -1 (electron-like) and those without charge (neutrinos).
The higher rest mass second and third generations of charged particles (quark and electron types) are only produced in extremely high-energy environments such as cosmic rays or particle accelerators. They are unstable and quickly decay into first generation particles. As a result, ordinary atomic matter is only composed of first generation particles: up and down quarks, and electrons.
Neutrinos are thought to have only very tiny masses, and it is thought that they dynamically oscillate from one flavor to another.
Photons have no rest mass or charge and have a spin of 1. They are gauge bosons - in gauge theory they are the carriers of the electromagnetic force and mediator of EM interactions among elementary particles. Please see http://en.wikipedia.org/wiki/Gauge_bosons. The properties of the W and Z bosons, carriers of the weak nuclear force, differ from photons only in that they have mass and mediate different force interactions.
Fundamentally, the flavors or generations of matter vary in their rest masses, while the EM force mediating photon has no rest mass - as I understand, photons with varying flavors of rest mass would be inconsistent with basic principles of the standard model.
Fermions have three generations e family is the lightest mu family
is heavier than e family and tau family is the heaviest. In fact the
heaviest quark of the third family (the top quark 175 GeV) is more massive
than the Higgs boson (125 GeV) which gives it a mass.
Photons are not fermions, they are bosons, meaning that they have
integral spin. In this case it is a spin one object. It mediates
electromagmetic force which is a long (infinite) range force.
Unless they are massless they cannot do this. Experimental
limits on photon mass are,
1. m ≲ 10^−14 eV/c^2 (tests of coulombs law)
2. m < 3×10^−27 eV/c^2 (astrophysical study of galactic plasma)
3. m
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