supported in part by the National Nature Science Foundations of China under contract numbers 11975028 and 10925522;by the Sino-German CRC 110(Grant No.TRR110)。
We give a pedagogical analysis on K-matrix models describing theπN scattering amplitude,in S11 channel at low energies.We show how the correct use of analyticity in the s-channel and crossing symmetry in t-and u-chan...
The project supported by National Natural Science Foundation of China under Grant Nos. 10075056 and 90103020 and the CAS Knowledge Innovation Project under Grant No. KC2-SW-N02.
Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S11 resonances, N(1535) and N(1650), and the helicity amplitudes A1...