Is the decay of a muon always a 1 to n process?

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    Decay Process
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Discussion Overview

The discussion centers around the nature of decay processes in particle physics, specifically questioning whether decay is always a ##1 \rightarrow n## process. Participants explore definitions of decay, the possibility of incoming particles appearing in the set of outgoing particles, and examples from beta decay and bremsstrahlung.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that decay processes typically start with one particle, suggesting a definition of decay that aligns with the ##1 \rightarrow n## model.
  • There is a question about whether an incoming particle can also be part of the outgoing particles, with some arguing that this would violate energy/momentum conservation.
  • One participant proposes that having the incoming particle in the outgoing set would require an intermediate stage and an external energy source, referencing beta decay as an example.
  • Another participant mentions that the process involving a muon and an antimuon could be considered annihilation rather than decay, as it does not fit the ##1 \rightarrow n## framework.
  • Bremsstrahlung is discussed, with participants debating whether it constitutes a decay process, noting that it involves scattering rather than a decay of a single particle.

Areas of Agreement / Disagreement

Participants express differing views on the definition of decay and whether processes can involve the same particle as both incoming and outgoing. The discussion remains unresolved, with multiple competing perspectives on the nature of decay processes.

Contextual Notes

Limitations include varying definitions of decay, the dependence on specific conditions for processes like beta decay, and the distinction between decay and scattering processes in particle interactions.

spaghetti3451
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Decay processes are quite common in particle physics.

Is the decay process always a ##1 \rightarrow n## process?

In other words, can we call the reaction $$\mu^{-} + \mu^{+} \rightarrow \phi,$$

where ##\phi## is some scalar particle, the decay of the muon?
 
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As a matter of definition, decay processes start with one particle.
 
Can we have the incoming particle also in the set of outgoing particles?
 
That would violate energy/momentum conservation.
 
failexam said:
Can we have the incoming particle also in the set of outgoing particles?
I believe this would require an intermediate stage, plus an external energy source. Consider neutron → proton → neutron transformation through beta decay:

β decay: when a free neutron decays into a proton

n → p + e + -νe

β+ decay: when a proton inside a nucleus decays into a neutron

p → n + e+ + νe

Note:
β+ decay cannot occur in an isolated proton because it requires energy due to the mass of the neutron being greater than the mass of the proton. β+ decay can only happen inside nuclei when the daughter nucleus has a greater binding energy (and therefore a lower total energy) than the mother nucleus.
 
failexam said:
where ϕ\phi is some scalar particle, the decay of the muon?
you call it annihilation of muon-antimuon...
obviously you don't have 1 muon to call it decay of the muon.
Can you have the incoming particle also in the outgoing particles? In vacuum as already mentioned no... but in other cases, yes, like Brehmstralung [itex]e \rightarrow e \gamma[/itex].
 
ChrisVer said:
like Brehmstralung [itex]e \rightarrow e \gamma[/itex].
Since the charged particle is only losing kinetic energy and its invariant mass remains unchanged, is this really considered decay?
 
stoomart said:
Since the charged particle is only losing kinetic energy and its invariant mass remains unchanged, is this really considered decay?
I didn't call it a decay- I gave that as an example to that you can have the same incoming and outgoing particle.
 
Of course bremsstrahlung is not a decay process since you always need the electron to scatter with something since a free electron won't radiate. Only accelerated charges radiate. So the correct bremsstrahlung process is a scattering process like ##\mathrm{e}^-+X \rightarrow \mathrm{e}^- + X +\gamma##, where ##X## is some particle or atomic nucleus scattering with the electron.
 

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