Do protons have excited states?

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Discussion Overview

The discussion revolves around whether protons and neutrons possess excited states, exploring the implications of different energy states and the nature of baryons, particularly Delta baryons, in relation to these states. Participants reference simulated shapes of protons and draw analogies to atomic physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if the different shapes of protons relate to various energy states.
  • Another participant compares Delta baryons to excited atomic states, suggesting they may represent excited states of protons and neutrons.
  • Some participants speculate about the existence of other excited states, possibly infinite, and their potential short-lived nature, drawing parallels to metastable states in atomic physics.
  • There is mention of a list of short-lived particles and resonances, indicating a lack of clear distinction between them.
  • A later reply clarifies that Delta baryons are not considered excited states of nucleons due to differing isospins, while noting the existence of numerous excited states of nucleons characterized by specific parameters.

Areas of Agreement / Disagreement

Participants express differing views on the classification of Delta baryons and the nature of excited states, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some statements rely on assumptions about the definitions of excited states and the characteristics of baryons, which may not be universally agreed upon. The discussion also touches on the complexities of particle classification and the transient nature of certain states.

Khashishi
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Do protons and neutrons have excited states?
This page shows some simulated shapes of protons. http://discovermagazine.com/2003/aug/breakprotons
Do the different shapes have to do with different energy states of the proton?
 
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Delta baryons are a bit like hadronic equivalents to excited atoms.

I'm not sure what the shapes are supposed to represent, and the description is not helpful in that respect. The ground state does not have to be a perfect sphere...
 
Interesting. If Delta^0 and Delta^+ are excited states of neutrons and protons, are there other (maybe infinite) excited states? Maybe they are too short-lived to be detected?
I suppose by analogy to atomic physics that the Delta states are metastable, sort of like metastable He triplet state. But it should be possible to get excited states with spin 1/2, right? Maybe it's too short-lived?
 
There are a lot of short-living particles and resonances (there is no clear line between them). The particle data group has a list of them (-> baryons -> N baryons and -> baryons -> Delta baryons).
 
Khashishi said:
Interesting. If Delta^0 and Delta^+ are excited states of neutrons and protons, are there other (maybe infinite) excited states? Maybe they are too short-lived to be detected?
I suppose by analogy to atomic physics that the Delta states are metastable, sort of like metastable He triplet state. But it should be possible to get excited states with spin 1/2, right? Maybe it's too short-lived?

The Deltas are not excited states of the nucleons because they have different isospins. but there are plenty of excited states of the nucleons typically listed as N(E)JP where E the (average) mass for the isospin multiplet measured in MeV, J is the total angular momentum and P is the Parity. For instance N(1440)1/2+ is the isospin doublet with average mass of 1440 MeVs, spin 1/2 and + parity. PDG lists about 30 of those excited states.
 
Khashishi said:
Do protons and neutrons have excited states?
This page shows some simulated shapes of protons. http://discovermagazine.com/2003/aug/breakprotons
Do the different shapes have to do with different energy states of the proton?

http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap06.pdf

Zz.
 

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