https://doi.org/10.1140/epjc/s10052-018-6024-5
Regular Article - Theoretical Physics
New insights on low energy 
scattering amplitudes
1
Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 100871, China
2
Instituto de Física Corpuscular (centro mixto CSIC-UV), Institutos de Investigación de Paterna, Apartado 22085, 46071, Valencia, Spain
3
Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
* e-mail: deliang.yao@ific.uv.es
Received:
28
March
2018
Accepted:
23
June
2018
Published online:
3
July
2018
The S- and P- wave phase shifts of low-energy pion-nucleon scatterings are analysed using Peking University representation, in which they are decomposed into various terms contributing either from poles or branch cuts. We estimate the left-hand cut contributions with the help of tree-level perturbative amplitudes derived in relativistic baryon chiral perturbation theory up to 
. It is found that in 
and 
channels, contributions from known resonances and cuts are far from enough to saturate experimental phase shift data – strongly indicating contributions from low lying poles undiscovered before, and we fully explore possible physics behind. On the other side, no serious disagreements are observed in the other channels.
© The Author(s), 2018
