Why do gluons and W and Z bosons have a limited range?

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Discussion Overview

The discussion revolves around the limited range of gluons and W and Z bosons compared to other particles like photons. Participants explore the underlying reasons for this phenomenon, touching on concepts from quantum mechanics and particle physics.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the limited range of W and Z bosons is due to their high mass and the uncertainty principle, which relates energy and time to spatial range.
  • One participant notes that gluons are massless but are confined due to their nature, although they express uncertainty about quantum chromodynamics (QCD).
  • Another participant explains that W and Z bosons can be created with sufficient energy in particle accelerators like the LHC, allowing them to exist outside of being virtual particles, but they still have a very short natural lifetime and decay into lighter products.
  • There is a discussion about the decay width of particles and its relation to their lifetime and range, with one participant attempting to clarify the definition of decay width.
  • Participants provide calculations related to the mass and decay properties of W and Z bosons, indicating their short ranges based on these properties.

Areas of Agreement / Disagreement

Participants express various viewpoints on the reasons for the limited range of gluons and W and Z bosons, with no consensus reached on a singular explanation. Some aspects are clarified, but uncertainty remains regarding certain concepts, particularly QCD and decay width.

Contextual Notes

Participants mention the uncertainty principle and decay width, but there are unresolved definitions and assumptions regarding these concepts. The discussion includes calculations that depend on specific values for mass and energy, which may not be universally agreed upon.

Bararontok
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Why do the gluon and W and Z boson particles have a limited range of movement, 10-15m for the gluon and 10-18m for the W and Z bosons, when the photon particles, gravitational force, and other particles have no limit to the distance they can travel?
 
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W and Z bosons are exchange bosons. The appear do there job and disapear again. The uncertainty pricinciple governs this. high mass short range. Gluons are confined by their nature. I will let someone else explain that one. The energy "borrowed" to create this particle must be "paid" back with a set time. Given these particles travel at neary the speed of light the follow is can be said.

Uncertainity principle states
ΔxΔp ≥ h/(4*pi) or

ΔEΔt ≥ h/(4*pi)

ΔEΔt = mc^2Δt ≥ h/(4*pi)

Virtual particles are traveling close to c so:

Range ≈ cΔt ≥ h/(4*pi*m*c)

Given the mass of a W boson is 80.4 Gev that works out to be 1.43E-25 kg. That gives a range of 1.2E-18 m. The same goes for the slightly ore massive Z boson.
 
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Gluons are massless so their confinement comes form another process. I do not understand QCD!
 
W and Z bosons are not always virtual. When they are created for example in the LHC, they have more than enough energy to put them on the mass shell. Even so they have an extremely short natural lifetime. The basic reason is that despite their large rest mass, they decay into lighter products. If you look up their properties at the Particle Data Group, you'll find that the W has a mass of 80 GeV and a width of 2 GeV. This corresponds to a range of about one-tenth of a fermi and a lifetime of 3 x 10-25 sec. Similarly the Z has a mass of 91 GeV and a width of 2.5 GeV.
 
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I think your reason is abit more exact and technical.

Decay width = h/(2*pi*t1/2) where t1/2 is half life. Putting 2.5 Gev into this gives you 2.63E-25 s which is right. Tavelling at ~c the range with half life is 7.9E-17m.

I am still trying to find an exact defination of decay width that makes sense though. there are no many explanations on the web and those that are present are very short an do explain in enough depth.

What do you mean by the mass shell as well?
 

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