Do protons have excited states?

  1. 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?
     
  2. jcsd
  3. mfb

    Staff: Mentor

    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...
     
  4. 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?
     
  5. mfb

    Staff: Mentor

    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).
     
  6. 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.
     
  7. ZapperZ

    ZapperZ 30,000
    Staff Emeritus
    Science Advisor
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