New insights on low energy πN scattering amplitudes: comprehensive analyses at level Supported in part by National Nature Science Foundations of China (NSFC)(10925522, 11021092), and by the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF)(FIS2017-84038-C2-1-P, FIS2017-84038-C2-2-P, SEV-2014-0398)
Yu-Fei Wang (Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China); De-Liang Yao (School of Physics and Electronics, Hunan University, Changsha 410082, China, Instituto de Física Corpuscular (centro mixto CSIC-UV), Institutos de Investigación de Paterna, Apartado 22085, 46071, Valencia, Spain); Han-Qing Zheng (Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China, Collaborative Innovation Center of Quantum Matter, Beijing 100871, China)
A production representation of partial-wave S matrix is utilized to construct low-energy elastic pion-nucleon scattering amplitudes from cuts and poles on complex Riemann sheets. Among them, the contribution of left-hand cuts is estimated using the results obtained in covariant baryon chiral perturbation theory within the extended-on-nass-shell scheme. By fitting to data on partial-wave phase shifts, it is indicated that the existences of hidden poles in S11 and P11 channels, as conjectured in our previous paper [Eur. Phys. J. C, 78(7): 543 (2018)], are firmly established. Specifically, the pole mass of the S11 hidden resonance is determined to be (895±81)−(164±23)i MeV, whereas, the virtual pole in the P11 channel locates at (966±18) MeV. It is found that analyses at the level improves significantly the fit quality, comparing with the previous one. Quantitative studies with cautious physical discussions are also conducted for the other S- and P-wave channels.
