Pion production by diffraction of W bosons in the dipole model

Abstract

In this work the scattering of neutrinos off heavy nuclei by exchange of W bosons in the color dipole model is studied, for small boson virtualities and energies of the order of some GeV’s. The first objective of this work is to analyze the black disc limit and to compare the results of the dipole model using perturbative light front wave functions with the ones of the meson model, which are vanishing because of lepton current conservation. Since both results differ, a more complete analysis is carried out, based on Glauber’s approach. At high energies, it is known that the color dipole model is well suited to study diffractive processes on nuclei, but at smaller energies the dipole lifetime is not large enough for the dipole to travel through the nucleus with a frozen transverse size. The short-lived dipoles are identified, and explicit calculations are carried out to determine if they have a large contribution to the final cross section. Although the model presents serious problems because of these short-lived asymmetric pairs, it provides a lower bound for the total cross section of pion production and it gives some additional hints that could be also of interest in more sophisticated models.