Effects of pairing correlation on s-wave scattering in superfluid nuclei are discussed. In the s-wave, single-particle potential resonance cannot be formed due to no potential barrier, whereas quasi-particle resonance can be formed by the pairing correlation. The quasi-particle resonance is a novel resonance in superfluid nuclei which is predicted by the Hartree-Fock-Bogoliubov (HFB) theory.
In recent progress of the SAMURAI experiments in RIKEN, characteristic s-wave peaks are observed in invariant mass spectroscopy of 21C. We anticipate that the s-wave peaks can be the s-wave quasi-particle resonance.
We analyze in detail how the low-lying s-wave quasi-particle resonance is governed by the pairing correlation in neutron drip-line nuclei. Solving the HFB equation in coordinate space with the scattering boundary condition, we calculate the phase shift, the elastic cross section, and the S-matrix. We find that the pairing correlation influence strongly the phase shift and the elastic cross section, in addition, four poles of S-matrix emerge by the pairing correlation. As a numerical example, we consider the 20C+n(s1/2) system to discuss the low-lying s-wave quasiparticle resonance.
In this presentation, we explain, using the S-matrix analysis, how the s-wave resonance caused by the pairing correlation (the s-wave quasi-particle resonance) emerge in neutron drip-line nuclei.