Neutrino,quark or any other particle? Is there any particle which is dimensionless,and without mass? Thanks for the answer.
At the quantum level, the concept of the "size" of a particle is somewhat fuzzy, due to the Heisenberg uncertainty principle. It currently appears that quarks, neutrinos and electrons (and other leptons) are not made up of anything more fundamental, so in that sense they are considered fundamental particles. Photons are one example of particles with no (rest) mass.
Thanks... I have only one question:Is there any of today's known particles dimension-less,quarks or any of all other particles known to today's science?
Quarks are point-sized. Photons are of size 0, due to the Lorentz contraction at the speed of light (c).
As I said, the concept of the size of a particle at the quantum level is not particularly well-defined. In interactions, quarks and photons tend to act pretty much as if they are dimensionless. (This has nothing to do with Lorentz contraction, though.)
