Role of pairing in the description of giant monopole resonances

We compare the results obtained in the framework of the quasiparticle random-phase approximation on top of a Hartree-Fock-Bogoliubov with the most recent experiments on giant monopole resonances in Pb, Sn, Zr, Sm, Mo, and Cd. Our calculations are fully self-consistent and the density dependence of pairing interactions is, for the first time in this framework, properly taken into account. In the particle-hole (ph) channel we employ different Skyrme functionals (SLy5, SkM* and Skxs20) while in the particle-particle (pp) channel we make use of density-dependent contact interactions. We introduce in the pp channel the recently proposed contact interactions which take into account the neutron-proton asymmetry. We find that no single parametrization is able to reproduce with sufficient accuracy all the nuclei. Since about two-thirds of the nuclei under investigation are better explained with a soft parametrization, this tends to suggest that the currently accepted picture for the incompressibility might require modifications.