Gluon is massless particle ,why strong interaction is short-range force?
There are two explanations.
Those that believe the universe is not discrete (i.e. they believe the there is such a thing as a continuum and a manifold), believe that the fields and dimensions involved are non-linear and/or curved near the nucleons.
i suspect the universe is discrete, and the stong nuclear force is because there is some alteration that occurs in one nucleon when it is near another, such as rotational phase. For example, it might be like tiny gears meshing their teeth when they are close, where the teeth are intervals (what we call gluon exchanges).
Because the strong interaction is non-abelian : gluons interact with themselves, and the vacuum screens the interaction at long distances. In the so called "dual superconducting model" or "flux tube" models, the potential grows enough at long distances to create new particles.
They are "masseless" only in a linear approximation. In fact the equations are strongly non-linear so the linear approximation is quite misleading. The interaction cannot be neglected without loss of essential physical effects (strong coupling). See, for example, "Reformulation instead of renormalizations" by Vladimir Kalitvianski (http://arxiv.org/abs/0811.4416).
Humanino's answer is correct - the gluons interact with themselves, so you get a different behavior than with photons which don't interact with themselves. As he points out, there are many models of this kind of behavior, but the details shouldn't obscure the main point: because of these self-interactions, the field falls off faster than 1/r2.
You don't need to posit a discrete universe (this behavior occurs without one) and the details of regularization are unimportant in understanding this.
The masses attributed to gluons and quarks cannot be used in the range relationship to predict the range of the force due to a property called confinement. That is. they are always contained within the proton or neutron. know that anything coming out of the nucleon is a quark antiquark pair and not a quark or gluon. It is the pion that is used to determine the range of the force and it's a lepton (still have mass).
No the pion is not a lepton
It is pion right and have a mass of 140 Mev and a range of 1.7fm according to Meson Theory.But they are not leptons intead they are Categorized as mesons of spin-0.
For reference request see Concepts of Modern Physics McGrawHill Arthur Beiser pages(410 and 482)
Thanks guy. I meant to say meson(this is obvious the mass accounts for the range. Infact we know that the strong interaction will not act between leptons since leptons have no color.
Guy you are good!
Separate names with a comma.