Pion-Mass Dependence of the N*(920) Subthreshold Nucleon Pole Trajectory
A study of how the subthreshold negative-parity nucleon pole N*(920), established in the S11 channel of pion-nucleon scattering, moves as the pion mass is varied. Working in the linear sigma model with nucleons and unitarizing via the N/D method (with Pade and K-matrix cross-checks), it finds the pole approaching the real axis as the pion mass grows: at tree level it lands on the logarithmic u-channel cut and crosses onto the adjacent Riemann sheet, while at one loop it stays off the u-cut up to m_pi = 0.36 GeV. The sigma pole trajectory is re-examined and agrees with Roy-equation analyses.
On the pole trajectory of the subthreshold negative parity nucleon with varying pion masses Qu-Zhi
We study the pole trajectory of the recently established subthreshold negative parity nucleon pole, namely the $N^*(920)$, with varying pion masses, in the scheme of linear $σ$ model with nucleons us…