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Title: Reconciling threshold and subthreshold expansions for pion–nucleon scattering

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 Δ(1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the Δ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the Δ-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.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [5] ;  [6]
  1. Ruhr Univ., Bochum (Germany). Inst. of Theoretical Physics II
  2. Univ. of Bonn (Germany). Helmholtz Inst. for Radiation and Nuclear Physics (Theory). Bethe Center for Theoretical Physics; Univ. of Bern (Switzerland). Albert Einstein Center for Fundamental Physics. Inst. for Theoretical Physics
  3. Ruhr Univ., Bochum (Germany). Inst. of Theoretical Physics II; Univ. of California, Santa Barbara, CA (United States). Kavli Inst. for Theoretical Physics
  4. Univ. of Washington, Seattle, WA (United States). Inst. for Nuclear Theory; Univ. of California, Santa Barbara, CA (United States). Kavli Inst. for Theoretical Physics
  5. Univ. of Bonn (Germany). Helmholtz Inst. for Radiation and Nuclear Physics (Theory). Bethe Center for Theoretical Physics
  6. Univ. of Bonn (Germany). Helmholtz Inst. for Radiation and Nuclear Physics (Theory). Bethe Center for Theoretical Physics; Forschungszentrum Julich (Germany). Inst. of Nuclear Physics. Inst. for Advanced Simulation. Julich Center for Hadron Physics
Publication Date:
Grant/Contract Number:
FG02-00ER41132; PHY-1125915; SFB/TR 16; DFGGSC 98/3; 2015VMA076
Type:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 770; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Research Org:
Univ. of Washington, Seattle, WA (United States); Ruhr Univ., Bochum (Germany); Univ. of Bonn (Germany); Univ. of Bern (Switzerland)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); National Science Foundation (NSF); German Research Foundation (DFG); Swiss National Science Foundation (SNSF); Chinese Academy of Sciences (CAS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; pion-baryon interactions; dispersion relations; chiral Lagrangians; chiral symmetries
OSTI Identifier:
1352704
Alternate Identifier(s):
OSTI ID: 1429069