The K-matrix approach to the Delta - resonance mass splitting and isospin violation in low-energy pi-N scattering

Abstract

The experimental data on pi N scattering in the elastic energy region T_pi < 250 MeV are analyzed within the multichannel K-matrix approach with effective Lagrangians. Isospin invariance is not assumed in this analysis and the physical values for masses of the involved particles are used. The corrections due to pi^+- pi^0 and p-n mass differences are calculated and found to be in a reasonable agreement with the NORDITA results. Analysis shows the good description of the all experimental observables. From the data, new values for mass and width of the Delta^0 and Delta^{++} resonances were obtained. The isospin symmetric version gives phase shifts values close to the new solution for the pi-N elastic scattering amplitude FA02 by the GW group based on the latest experimental data. Our analysis leads to a considerably smaller < 1% isospin violation in the energy interval T_pi ~ 30-70 MeV as compared to 7% in some older analyses, however, it does confirm recent calculations based on chiral perturbation theory.

arXiv comment13 pages, 8 figures, Phys. At. Nucl. and Yad. Fiz.(2005)

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• The ratios of the light quark masses
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• Differential cross section of the pion-nucleon charge-exchange reaction in the momentum range from 148 to 323 MeV/c
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Cited by in corpus (11)

• Delta-excitations and the three-nucleon force
• Extracting the sigma-term from low-energy pion-nucleon scattering
• Photocouplings at the Pole from Pion Photoproduction
• Isospin violation in low-energy pion-nucleon scattering revisited
• Nucleon resonance parameters from Roy-Steiner equations
• Electromagnetic mass differences of SU(3) baryons within a chiral soliton model
• Isospin splittings in the decuplet baryon spectrum from dynamical QCD+QED
• Differential cross sections of the charge-exchange reaction pi- p --> pi0 n in the momentum range from 103 to 178 MeV/c
• Test of isospin symmetry via low energy ${}^1$H(${\pi }^{-}$,${\pi }^o$)$n$ charge exchange
• Complex phase structure of the meson-baryon $T$-matrix
• Mass and Isospin Breaking Effects in the Skyrme Model and in Holographic QCD