Do Pions Exist Naturally in High Z Nuclei and How Do Their Half Lives Change?

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    Nuclei Pions
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Discussion Overview

The discussion revolves around the existence of pions in high atomic number (Z) nuclei, their stability, and how their half-lives may be affected in bound states. Participants explore theoretical implications and experimental observations related to pions in nuclear physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question whether pions exist naturally in high Z nuclei or if they are only produced in scattering experiments.
  • There is a suggestion that the half-lives of pions may increase when they are bound within a nucleus, although the extent of this increase is debated.
  • One participant notes that the energy gain of a pion inside a nucleus is comparable to that of nucleons, but still insufficient to make pions stable.
  • A conjecture about "Strange Matter" is introduced, proposing that baryons with strange quarks could stabilize heavy nuclei, though no evidence has been found for such matter.
  • Another participant asserts that no stable nuclei contain pions, and while the half-lives of pions may be slightly longer in a nucleus, the increase is minimal.
  • It is mentioned that the charge of the pion does not affect its interaction with nucleons due to the attractive nature of the strong force.

Areas of Agreement / Disagreement

Participants express differing views on the existence of pions in natural settings versus experimental conditions, as well as the implications of their half-lives in bound states. The discussion remains unresolved regarding the stability of pions within nuclei.

Contextual Notes

Limitations include uncertainties about the conditions under which pions may exist in nuclei and the specific definitions of stability and half-life in this context.

Kevin McHugh
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Do they exist in nature, i.e. in high Z nuclei, or are they only created in scattering experiments? Are the half lives increased in bound states? Why do positive pions get trapped in the potential well as well as negative pions?
 
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The energy gain of a pion inside the nucleus is comparable to that of a neutron or proton. Usually it's more because the pion doesn't pay exchange energy. But it's still one order or magnitude less than what would be required to make the pion stable.
People conjectured Strange Matter where baryons containing strange quarks are incorporated into an extremely heavy nucleus, which could stabilize both the nucleus and the strange baryons. But so far no one has found any of that stuff.
 
TTT. Thanks for the reply Gigaz, but that doesn't really answer my questions.
 
There are no stable nuclei that contain pions. All known stable nuclei contain only neutrons and protons.
The half-lifes of pions should be somewhat larger when the pion is inside a nucleus, but not by more than a few percent.
The charge of the pion doesn't matter because it doesn't matter for protons. The interaction is always attractive because it is mediated via the strong force.
 
Thanks Gigaz. That helps a lot.
 

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