The charge distribution of a proton is characterized by a positive core surrounded by a negative pion cloud
the verdict
SUPPORTED
the evidence backs this
refutedsupported
the weight of evidence
2 sources for · 0 against
Peer-reviewed literature and physical models indicate that the proton's structure includes a central core surrounded by an outer region or cloud of virtual mesons, specifically consistent with a pion cloud description.
A Coherent Interpretation of the Form Factors of the Nucleon in Terms of a Pion Cloud and Constituent Quarks
The recent unbiased measurements of the electric form factor of the neutron suggest that its shape may be interpreted as a smooth broad distribution with a bump at Q^2 \approx 0.3(GeV/c)^2 superimposed. As a consequence the corresponding charge distribution in the Breit frame shows a negative charge extending as far out as 2fm. It is natural to identify this charge with the pion cloud. This realisation is then used to reanalyse all old and new data of the electric and magnetic from factors of the proton and the neutron by a phenomenological fit and by a fit based on the constituent quark model. It is shown that it is possible to fit all form factors coherently with both ansaetzen and that they all show the signal of the pion cloud.
Published as: Eur.Phys.J.A17:607-623,2003
DOI: 10.1140/epja/i2003-10025-3
arXiv categories: hep-ph
That configuration, which may be interpreted as a pion loop ("cloud") fluctuation, also leads to a clearly better description of the nucleon magnetic moments. When the amplitude of the sea-quark admixtures are set so as to describe the electric form factor of the neutron, the qqqq\bar q admixtures have the phenomenologically desirable feature, that the electric form factor of the proton falls at a more rapid rate with momentum transfer than the magnetic form factor. Published as: Nucl.Phys.A791:406-421,2007
DOI: 10.1016/j.nuclphysa.2007.05.002
arXiv categories: nucl-th
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