@article{Siemens2017,
abstract = {Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion–nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the $\Delta$(1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the $\Delta$ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the $\Delta$-less theory the resummation of 1/mN corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.},
archivePrefix = {arXiv},
arxivId = {1610.08978},
author = {Siemens, D. and {Ruiz de Elvira}, J. and Epelbaum, E. and Hoferichter, M. and Krebs, H. and Kubis, B. and Mei{\ss}ner, U. G.},
doi = {10.1016/j.physletb.2017.04.039},
eprint = {1610.08978},
issn = {03702693},
journal = {Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics},
keywords = {Chiral Lagrangians,Chiral symmetries,Dispersion relations,Pion–baryon interactions},
pages = {27--34},
title = {{Reconciling threshold and subthreshold expansions for pion–nucleon scattering}},
volume = {770},
year = {2017}
}

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We find that the inclusion of the $\\Delta$ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the $\\Delta$-less theory the resummation of 1/mN corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.","archiveprefix":"arXiv","arxivid":"1610.08978","author":[{"propositions":[],"lastnames":["Siemens"],"firstnames":["D."],"suffixes":[]},{"propositions":[],"lastnames":["Ruiz de Elvira"],"firstnames":["J."],"suffixes":[]},{"propositions":[],"lastnames":["Epelbaum"],"firstnames":["E."],"suffixes":[]},{"propositions":[],"lastnames":["Hoferichter"],"firstnames":["M."],"suffixes":[]},{"propositions":[],"lastnames":["Krebs"],"firstnames":["H."],"suffixes":[]},{"propositions":[],"lastnames":["Kubis"],"firstnames":["B."],"suffixes":[]},{"propositions":[],"lastnames":["Meißner"],"firstnames":["U.","G."],"suffixes":[]}],"doi":"10.1016/j.physletb.2017.04.039","eprint":"1610.08978","issn":"03702693","journal":"Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics","keywords":"Chiral Lagrangians,Chiral symmetries,Dispersion relations,Pion–baryon interactions","pages":"27–34","title":"Reconciling threshold and subthreshold expansions for pion–nucleon scattering","volume":"770","year":"2017","bibtex":"@article{Siemens2017,\nabstract = {Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion–nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the $\\Delta$(1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the $\\Delta$ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the $\\Delta$-less theory the resummation of 1/mN corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.},\narchivePrefix = {arXiv},\narxivId = {1610.08978},\nauthor = {Siemens, D. and {Ruiz de Elvira}, J. and Epelbaum, E. and Hoferichter, M. and Krebs, H. and Kubis, B. and Mei{\\ss}ner, U. 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