Nuclear Structure Functions from a Chiral Soliton

por Dr. H. Weigel (Universidad de Tuebingen)

miércoles 19 nov. 1997 12:00 → 13:00 Europe/Madrid

Sala Seminarios (Dpto. de Fisica Teorica (UVEG))

We study nucleon structure functions within the bosonized Nambu--Jona--Lasinio (NJL) model where the nucleon emerges as a chiral soliton. This attempts at merging the parton model description of deep inelastic scattering with the phenomenologically successful picture of baryons as chiral solitons. As examples we present the unpolarized structure functions for the $\nu p$ and $\bar \nu p$ scattering in the valence quark approximation which is formulated such that the Adler sum rule is satisfied. This approximation is justified for moderate constituent quark masses ($\sim 400 \rm MeV $) for which the contribution of the valence quark level dominates the nucleon properties. We also discuss the model predictions on the Gottfried sum rule for electron nucleon scattering. A comparison with a low--scale parametrization shows that the model reproduces the gross features of the empirical structure functions. In addition the issues of projection and $q^2$--evolution are addressed thereby determining the intrinsic scale $\mu^2$ of the NJL model. We also compute the leading twist contributions of the polarized structure functions $g_1$ and $g_2$ in this model. We compare the model predictions on these structure functions with data from the E143 experiment by evolving them from the scale $\mu^2$ characteristic for the NJL-model to the scale of the data. For this purpose a leading order GLAP procedure is employed. Finally we include a discussion on the projection of the model structure functions. The projection is mandatory for localized field configurations to enforce consistency with Lorentz--covariance.