Near threshold electroproduction of theωmeson atQ2≈0.5GeV2

Neutral-pion electroproduction on the proton near threshold.

The neutral pion electroproduction on the proton is considered in the framework phenomenological model based on the PCAC, current algebra with hard pions and chiral symmetry breaking interaction. The swave differential cross-section of the electroproduction of neutral pions off protons near the threshold is predicted as function photon momentum transfer squared k2 . The swave multipoles ReE0+ a...

Threshold pion electroproduction at large momentum transfers

Near threshold neutral pion electroproduction on deuterium in chiral perturbation theory

Near threshold neutral pion electroproduction on the deuteron is studied in the framework of baryon chiral perturbation theory at next–to–leading order in the chiral expansion. We develop the multipole decomposition for pion production off spin-1 particles appropriate for the threshold region. The existing data at photon virtuality k = −0.1GeV can be described satisfactorily. Furthermore, the p...

Improved Description of Threshold Pion Electroproduction in Chiral Perturbation Theory

We investigate neutral pion electroproduction off protons in the framework of heavy baryon chiral perturbation theory. The chiral expansion of the S–wave multipoles E0+ and L0+ is carried out to three orders. There appear several undetermined low– energy constants. Three are taken from a recent study of the new TAPS threshold π0 photoproduction data, one is fixed from the proton Dirac form fact...

THRESHOLD TWO–PION PHOTO – AND ELECTROPRODUCTION: More neutrals than expected

We present an exploratory study of two pion photo– and electroproduction off the nu-cleon in the threshold region. To calculate the pertinent amplitudes, we make use of heavy baryon chiral perturbation theory. We show that due to finite chiral loops the production cross section for final states with two neutral pions is considerably enhanced. The experimental implications are briefly discussed.