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

[Kevin McHugh]

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?

 

[Gigaz]

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.

 

[Kevin McHugh]

TTT. Thanks for the reply Gigaz, but that doesn't really answer my questions.

 

[Gigaz]

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.

 

[Kevin McHugh]

Thanks Gigaz. That helps a lot.