Threshold pion electro- and photoproduction off nucleons in covariant chiral perturbation theory

Abstract

Pion electro-and photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O(p 3 ) in the extended-on-mass-shell scheme, with the explicit inclusion of the ∆(1232) resonance. The relevant low energy constants are fixed by fitting the available experimental data with the theoretical model. The inclusion of the ∆ resonance as an explicit degree of freedom substantially improves the agreement with data and the convergence of the model.

Dispersive analysis of low energy $γ^* N\rightarrowπN$ process

“…Different from Ref. [17,20], here we go beyond pure χPT calculations by applying the final state interaction theorem to partial wave amplitudes. To pin down the free parameters in the dispersive amplitude, we perform fits to experimental data of multipole amplitudes E 0+ and S 0+ for the energies ranging from πN threshold to 1.440 GeV 2 .…”

“…The results are listed in the Appendix A. for higher order O(p 3 ) contributions and the influence of ∆(1232) resonance, readers can refer to Ref. [20].…”

“…Since 1980s, it has been successful to explore the electroproduction and relevant processes using chiral perturbation theory (χPT) at low energies [16][17][18][19][20]. For the calculation of loop diagrams, there are several renormalization schemes, which are e.g.…”

“…[16] and EOMS scheme adopted in Refs. [17,20], to solve the power-counting breaking (PCB) problems. However, χPT only works well near the threshold and fails at slightly higher energies.…”

Radiative Correction to Lepton Proton Scatterings in Manifestly Lorentz-Invariant Chiral Perturbation Theory

“…The recent papers of considering ∆(1232) in the low energy hadron scatterings can be found in Refs. [38][39][40].…”