Bosons massless photon

The electron (e), the muon (/i) and the tauon (r) are electric charge carrying members of the leptons, while their corresponding neutrinos and are electrically neutral. The charged leptons together with the quarks can interact with each other via exchange of a massless vector boson, the photon (7), which is the carrier of the electromagnetic interaction. 

We now consider the choice of the scalar fields. Since we desire to end up with three heavy vector bosons associated with the weak interactions and a massless vector boson, the photon, we require 3-1-1 = 4 independent scalar fields. The simplest choice (sometimes referred to as the minimal SM) is a doublet of complex scalar fields, one charged, one neutral ... 

For simplicity, we consider the universe to be radiation dominated. This is because the particles, even the highly massive X, Y, and V particles have such large kinetic energies that they behave similar to photons or massless bosons. This state of affairs in the early universe was know to exist up until the universe dropped to a temperature below 103 K 100,000 years into its evolution. For the radiation dominated period in the evolution of the universe the pressure and density were related by... 

Entities that move in the interface are achiral and massless. A virtual photon consists of a virtual particle/anti-particle pair. The vector bosons that mediate the weak interaction are massive and unlike photons, distinct from their anti-particles. The weak interaction therefore has reflection symmetry only across the vacuum interface and hence /3-decay violates parity conservation. 

W boson (W particle) Either of a pair of elementary particles (W or W ), classified as intermediate vector bosons, that are believed to transmit the weak interaction (see FUNDAMENTAL INTERACTIONS) in much the same way as photons transmit the electromagnetic interaction. They are not, however, massless like photons, and are believed to... 

As there is a one-to-one correspondence between the dimension of the group and the number of massless gauge fields that are necessary to attain gauge invariance, and, since the only known massless vector boson is the photon, it might appear that non-Abelian gauge qonmetries just define an elegant formalism that has very little to do with physics. 

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