Quark-antiquark creation in strong interactions

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Discussion Overview

The discussion revolves around the process of quark-antiquark creation in strong interactions, specifically focusing on the decay of the Δ+ baryon into a neutron and a pion. Participants explore the conservation laws involved and the mechanics of quark transformations during this decay process.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions how a three-quark particle (Δ+) can decay into two particles that collectively contain five quarks, expressing confusion over the conservation of quark numbers.
  • Another participant suggests that the decay involves a down quark emitting a gluon, which then creates a quark-antiquark pair, indicating that the process is effectively a transformation from one quark to three quarks.
  • There is a clarification that the quark-antiquark pair produced by the gluon does not need to be of the same type, but it cannot be mixed, leading to a discussion about the specific quark content of the resulting particles.
  • Participants discuss the correct identification of the pion types involved in the decay process, with one initially misidentifying the pion and later correcting it.
  • A later reply confirms the understanding that the Δ+ decays into a neutron and a pion through the emission of a gluon that produces a down quark-antidown quark pair, with the down quark going to the neutron and the antidown quark joining with an up quark to form the pion.

Areas of Agreement / Disagreement

Participants generally agree on the mechanics of the decay process and the role of gluons in creating quark-antiquark pairs, but there are initial misunderstandings regarding charge conservation and the types of pions involved. The discussion reflects a mix of confusion and clarification without a definitive consensus on all aspects.

Contextual Notes

There are unresolved questions about the specifics of quark transformations and the implications of conservation laws in this decay process. Some assumptions about quark types and interactions remain implicit and are not fully explored.

sunrah
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(please note this is similar to a homework question I have posted but it is not the same and here I am just trying to understand a concept)

In a book I was reading it said

[itex] \Delta^{+} \longrightarrow n + \pi^{+}[/itex]

is a viable process via the strong force because all that is needed is a down antidown quark pair, which can be provided via the strong force. My question is why? If [itex]\Delta^{+}[/itex] is uud and [itex]\Delta^{+}\pi^{+}[/itex] is udd + [itex]u\bar{d}[/itex] we can see that the right hand side only has one antidown quark therefore there has only been one quark-antiquark pair created. Converting one quark into two only creates one extra particle effectively so I see a deficit on the left hand side.

Please can someone explain
 
Last edited:
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Δ+ → n + π0

:confused: What you have written does not conserve charge.
 
Bill_K said:
:confused: What you have written does not conserve charge.

You're right. I've changed it now it. My question really is about how a 3 quark particle can become two particles with a total of 5 quarks :smile:

we don't do this stuff in lectures
 
The process would be

d -> d + g -> d + (q qbar)

A gluon gets emitted that then decays. You're thinking its one d decaying to two, when its really 1 to 3
 
Hepth said:
The process would be

d -> d + g -> d + (q qbar)

A gluon gets emitted that then decays. You're thinking its one d decaying to two, when its really 1 to 3

oh I see. does the q-qbar-pair have to be the same type? If I understand it right in this case the gluon must become an up and an antidown pair.
 
The q can be anything, but not mixed. A pi0 is not u dbar. It is u ubar and d dbar.
 
Hepth said:
The q can be anything, but not mixed. A pi0 is not u dbar. It is u ubar and d dbar.

sorry my question was wrong. it should have been pi+ :redface:

does this mean this process is forbidden?
 
I'll write ubar as u~

You have
uud > udd + ud~
So quark content is fine.

Draw it out, the gluon makes a d d~ but the d goes to the neutron, the d~ to the pion.
 
I think it just went click.
The Delta+ decays into two parts (e.g. ud and u) thereby producing a gluon which becomes dd~ pair except the d is taken up by ud to form a neutron and d~ joins with u to form a pi+.

Is that more or less right?
 
  • #10
Yes that is correct.
 

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