Pion photoproduction in chiral perturbation theory with explicit treatment of the $Δ(1232)$ resonance

Abstract

We study the reaction of pion photoproduction on the nucleon in the framework of chiral perturbation theory with explicit ∆(1232) degrees of freedom. In the covariant approach, we give results up to order 3 in the small scale expansion scheme. Furthermore, we provide ∆-less and ∆-full results obtained in the heavy-baryon scheme to analyze the differences to the covariant approach. Low energy constants are fitted to multipole amplitudes using theoretical truncation errors estimated by a Bayesian approach. We also compare our findings to data of neutral pion production cross sections and polarization asymmetries. The description of the reaction is clearly improved by the explicit treatment of the ∆(1232) resonance.

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].…”

Light-quark mass dependence of the nucleon axial charge and pion-nucleon scattering phenomenology

“…Alternatively, LECs have been extracted from experimental information 3 on various processes such as pion photoand electroproduction [13][14][15][16] but, predominantly, from pion-nucleon (πN ) scattering [17][18][19][20][21][22][23][24][25]. Although d 16 cannot be extracted from πN elastic scattering, it contributes significantly to inelastic, πN → ππN , scattering.…”

Gaussian process error modeling for chiral effective-field-theory calculations of $np\leftrightarrow dγ$ at low energies

“…In this work, we present the first χEFT results for the energy-dependent np ↔ dγ cross section for a range of energies from threshold to MeV scale, that encompasses the BBN regime. We extend the Bayesian procedure for estimating the χEFT truncation error, which was earlier applied to various other observablesnucleon-mass expansion [2,5], nucleon-nucleon elastic scattering [4,7,8,13,19], nucleon-deuteron scattering [16,18], nuclear-matter equation of state [42,43], pion-photoproduction on the nucleon [21,25], and properties of light nuclei [20,22]-to an electromagnetic reaction cross section. We adopt the error model developed by Melendez et al [13] that used machine learning with Gaussian processes (GPs) calibrated by physics-based hyperparameters to determine the convergence of EFT predictions that may be correlated across independent variables (e.g., energy).…”