Journal
PHYSICS LETTERS B
Volume 770, Issue -, Pages 27-34Publisher
ELSEVIER
DOI: 10.1016/j.physletb.2017.04.039
Keywords
Pion-baryon interactions; Dispersion relations; Chiral Lagrangians; Chiral symmetries
Funding
- DFG [SFB/TR 16]
- DOE [DE-FG02-00ER41132]
- National Science Foundation [NSF PHY-1125915]
- Swiss National Science Foundation
- Ruhr University Research School PLUS - Germany's Excellence Initiative [DFG GSC 98/3]
- Chinese Academy of Sciences (CAS) President's International Fellowship Initiative (PIFI) grant [2015VMA076]
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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 A(1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the A 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/m(N) 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. (C) 2017 The Authors. Published by Elsevier B.V.
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