https://doi.org/10.1140/epja/i2006-10235-1
Regular Article - Hadron Physics
Electromagnetic polarizabilities and the excited states of the nucleon
Zweites Physikalisches Institut der Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
* e-mail: mschuma3@gwdg.de
Received:
30
November
2006
Accepted:
9
February
2007
Published online:
29
March
2007
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 –
© Società Italiana di Fisica and Springer-Verlag, 2007
