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The European Physical Journal A

, Volume 31, Issue 3, pp 327–333 | Cite as

Electromagnetic polarizabilities and the excited states of the nucleon

  • M. SchumacherEmail author
Regular Article - Hadron Physics

Abstract.

The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α p(E 0+) = + 3.2, α n(E 0+) = + 4.1, the t-channel α t p, n = - β t p, n = + 7.6 and the resonant β p, n(P 33(1232)) = + 8.3 contributions (in units of 10-4fm^3). The remaining deviations from the experimental data Δα p = 1.2±0.6, Δβ p = 1.2±0.6, Δα n = 0.8±1.7 and Δβ n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions. This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms of two-photon coupling to the σ-meson having the predicted mass m σ = 666MeV and two-photon width Γ γγ = 2.6keV.

PACS.

11.55.Fv Dispersion relations 11.55.Hx Sum rules 13.60.Fz Elastic and Compton scattering 14.70.Bh Photons 

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Copyright information

© Società Italiana di Fisica and Springer-Verlag 2007

Authors and Affiliations

  1. 1.Zweites Physikalisches Institut der Universität GöttingenGöttingenGermany

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