# Why we need intermediate particles

• spidey
In summary, virtual particles such as W and Z bosons are necessary in understanding and describing interactions in quantum field theory. While the original Fermi theory did not include particle exchange, the unified electroweak theory with W and Z exchange bosons emerged in the late 1960s and has been supported by experiments in the 1980s. These virtual particles play a crucial role in explaining the behavior of particles in various processes and are consistent with special relativity and quantum mechanics.
spidey
why we need intermediate particles? i.e. why we want virtual particles like w,z boson etc..
for example,in the beta minus decay..neutron is converted into proton+electron+neutrino...
n-> p + e + ne
then we why want something intermediate w- like this
n-> p + w- -> p + e + ne

both are same only..then why we want w-...

we can write
0 = 1 -1
or
0 = 1 + a where a = -1 + 0
both are same..we can write many equations like this..

I am confussed ..can someone explain?

the physics going on is not n-> p + e + ne .. that is just counting. If you want to understand and describe why and how the neutron decays, one needs formulas which are consistent with special relativity and quantum mechanics. And then one developed quantym field theory. And in quantumm field theory, the interaction will be described by, if you do a perturbative series expansion of the S-matrix, a sum of such intermediate states with a (or several) virtual particle(s) mediating the interaction.

You can get some introductory material on this, with math, if you PM me.

Last edited:
malawi_glenn said:
the physics going on is not n-> p + e + ne .. that is just counting. If you want to understand and describe why and how the neutron decays, one needs formulas which are consistent with special relativity and quantum mechanics. And then one developed quantym field theory. And in quantumm field theory, the interaction will be described by, if you do a perturbative series expansion of the S-matrix, a sum of such intermediate states with a virtual particle mediating the interaction.

You can get some introductory material on this, with math, if you PM me.

many thanks..i PMed u..

The original theory of the weak interaction put forth by Fermi in the early 1930s did not include particle exchange. Even for some time after the unified electroweak theory (Weinberg-Salam) with W and Z exchange bosons appeared in the late 1960s, the Fermi theory could adequately describe accelerator experiments involving neutrinos etc., at the energies that were available then. This was the case when I was in graduate school in the 1970s. Finally in the 1980s energies increased to the point where Fermi theory and Weinberg-Salam gave measurably different predictions, and experiments supported the newer theory.

it was just a point interaction in Fermi theory, and indeed many weak decays can be well approximated as Fermi decay, such as muon decay.

But I think OP was after the more general stuff, in any process, why need for virtual particles.

## 1. Why do we need intermediate particles?

Intermediate particles, also known as gauge bosons, are necessary in the Standard Model of particle physics to mediate the fundamental forces between particles. These forces include the strong nuclear force, weak nuclear force, and electromagnetic force. Without these intermediate particles, particles would not be able to interact with each other, leading to a universe that looks drastically different from the one we observe.

## 2. What are the functions of intermediate particles?

The specific functions of intermediate particles vary depending on the force they mediate. For example, gluons mediate the strong nuclear force, which holds atomic nuclei together, while photons mediate the electromagnetic force, which allows for the interaction between charged particles. The W and Z bosons mediate the weak nuclear force, responsible for radioactive decay.

## 3. How do intermediate particles interact with matter?

Intermediate particles interact with matter through the exchange of energy and momentum. When two particles interact, they exchange intermediate particles, which carry the force between them. These intermediate particles are responsible for transferring the force from one particle to another, allowing for the interaction between particles.

## 4. Can intermediate particles be observed?

Intermediate particles cannot be directly observed due to their short lifetimes and high energies. However, their presence can be inferred through the effects they have on other particles. For example, the discovery of the Higgs boson in 2012 provided evidence for the existence of the Higgs field, which gives particles mass through interactions with the Higgs boson.

## 5. Are intermediate particles related to dark matter?

No, intermediate particles are not related to dark matter. Dark matter is a hypothesized type of matter that does not interact with light and has not been directly observed. Intermediate particles, on the other hand, are a well-established part of the Standard Model of particle physics and have been observed and studied in experiments such as the Large Hadron Collider.

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