Nucleon Electroweak Form Factors: Analysis of Their Spectral Functions
نویسندگان
چکیده
We investigate the imaginary parts of the nucleon electromagnetic and axial form factors close to threshold in the framework of heavy baryon chiral perturbation theory. For the isovector electromagnetic form factors, we recover the well known strong enhancement near threshold. For the isoscalar ones, we show that there is no visible enhancement due to the three–pion continuum. This justifies the use of vector meson poles only in dispersion–theoretical calculations. We also calculate the imaginary part of the nucleon isovector axial form factor and show that it is small in the threshold region. #1Address after Oct. 1, 1996: FZ Jülich, IKP (Theorie), D-52425 Jülich, Germany
منابع مشابه
Isospin-breaking corrections to nucleon electroweak form factors in the constituent quark model.
We examine isospin breaking in the nucleon wave functions due to the u−d quark mass difference and the Coulomb interaction among the quarks, and their consequences on the nucleon electroweak form factors in a nonrelativistic constituent quark model. The mechanically induced isospin breaking in the nucleon wave functions and electroweak form factors are exactly evaluated in this model. We calcul...
متن کاملSpectral functions of isoscalar scalar and isovector electromagnetic form factors of the nucleon at two-loop order
We calculate the imaginary parts of the isoscalar scalar and isovector electromagnetic form factors of the nucleon up to two-loop order in chiral perturbation theory. Particular attention is paid on the correct behavior of Im σN (t) and Im GE,M (t) at the two-pion threshold t0 = 4mπ in connection with the non-relativistic 1/M -expansion. We recover the well-known strong enhancement near thresho...
متن کاملNucleon axial charge and structure functions with domain wall fermions
Domain wall fermions (DWF) [1] have been successfully used by the RBC Collaboration for several applications [2]. In the baryon sector we had reported that DWF with Wilson gauge action in the quenched approximation can reproduce the first negative-parity excited state of nucleon [3] which defied theoretical attempts for a long time. Here we report the current status of our calculations on the n...
متن کاملNucleon electroweak form factors in a meson-cloud model
The meson-cloud model of the nucleon consisting of a system of three valence quarks surrounded by a meson cloud is applied to study the electroweak structure of the proton and neutron. The electroweak nucleon form factors are calculated within a light-front approach, by obtaining an overall good description of the experimental data. Charge densities as a function of the transverse distance with...
متن کاملNucleon Form Factors in Dispersion Theory
Dispersion relations provide a powerful tool to analyse the electromagnetic form factors of the nucleon both in the space-like and time-like regions with constraints from other experiments, unitarity, and perturbative QCD. We give a brief introduction into dispersion theory for nucleon form factors and present first results from our ongoing form factor analysis. We also calculate the two-pion c...
متن کامل