Role of the rho meson in the description of pion electroproduction experiments at JLab

TL;DR

This paper investigates the role of the rho meson in pion electroproduction at JLab, demonstrating that including the rho-meson t-pole contribution, especially in tensor representation, improves agreement with experimental data and affects form factor extraction.

Contribution

It introduces a detailed effective Lagrangian model with rho meson degrees of freedom, highlighting the significance of the tensor representation and rho-meson t-pole contributions in describing experimental data.

Findings

Tensor representation of rho meson better fits data.

Rho-meson t-pole contribution improves cross section description.

Soft form factors are compatible with data.

Abstract

We study the p(e,e' pi+)n reaction in the framework of an effective Lagrangian approach including nucleon, pi and rho meson degrees of freedom and show the importance of the rho-meson t-pole contribution to sigmaT, the transverse part of cross section. We test two different field representations of the rho meson, vector and tensor, and find that the tensor representation of the rho meson is more reliable in the description of the existing data. In particular, we show that the rho-meson t-pole contribution, including the interference with an effective non-local contact term, sufficiently improves the description of the recent JLab data at invariant mass W less 2.2 GeV and Q2 less 2.5 GeV2/c2. A ``soft'' variant of the strong piNN and rhoNN form factors is also found to be compatible with these data. On the basis of the successful description of both the sigmaL and sigmaT parts of the cross section we discuss the importance of taking into account the sigmaT data when extracting the charge pion form factor Fpi from sigmaL.