Upper Energy Limit of Heavy Baryon Chiral Perturbation Theory in Neutral Pion Photoproduction

Abstract

With the availability of the new neutral pion photoproduction from the proton data from the A2 and CB-TAPS Collaborations at Mainz it is mandatory to revisit Heavy Baryon Chiral Perturbation Theory (HBChPT) and address the extraction of the partial waves as well as other issues such as the value of the low-energy constants, the energy range where the calculation provides a good agreement with the data and the impact of unitarity. We find that, within the current experimental status, HBChPT with the fitted LECs gives a good agreement with the existing neutral pion photoproduction data up to $\sim$170 MeV and that imposing unitarity does not improve this picture. Above this energy the data call for further improvement in the theory such as the explicit inclusion of the Δ(1232). We also find that data and multipoles can be well described up to $\sim$185 MeV with Taylor expansions in the partial waves up to first order in pion energy.

6 pages, 5 figures, version to be published in Physics Letters B

References in corpus (8)

• Chiral perturbation theory
• Isospin breaking in the pion-nucleon scattering lengths
• Accurate Test of Chiral Dynamics in the \boldmath$\vec{\gamma }p\to {\pi }^{0}p$ Reaction
• Threshold ${\pi }^0$ photoproduction in relativistic chiral perturbation theory
• Properties of Nucleon Resonances by means of a Genetic Algorithm
• Low-Energy D-Wave Effects in Neutral Pion Photoproduction
• Operator Approach to Isospin Violation in Pion Photoproduction
• The Upper Energy Limit of HBChPT in Pion Photoproduction

Cited by in corpus (13)

• QCD and strongly coupled gauge theories: challenges and perspectives
• Photocouplings at the Pole from Pion Photoproduction
• Accurate Test of Chiral Dynamics in the \boldmath$\vec{\gamma }p\to {\pi }^{0}p$ Reaction
• Model Selection for Pion Photoproduction
• Neutral-current weak pion production off the nucleon in covariant chiral perturbation theory
• Pion photoproduction off nucleons in covariant chiral perturbation theory
• $\Delta (1232)$ resonance in the $\vec{\gamma }p\to p{\pi }^0$ reaction at threshold
• Threshold pion electro- and photoproduction off nucleons in covariant chiral perturbation theory
• A precision measurement of the $p$($e,e^{\prime }p$)${\pi }^0$ reaction at threshold
• New Analysis of Threshold Photoproduction Data from MAMI
• Symmetry Tests in Photo-Pion Production
• The Upper Energy Limit of HBChPT in Pion Photoproduction
• Threshold Neutral Pion Photoproduction on the Proton