Giant resonances in $^{112 \sim124}$Sn isotopes and the symmetry term in nuclear

Based on the same data on the giant monopole resonances, calculations within the non-relativistic and relativistic models predict for nuclear incompressibility $K_\infty$ values which are significantly different from one another, \textit{viz.}$\approx$220-235 and $\approx$250-270 MeV respectively. It appears that the solution of this puzzle requires a better determination of the symmetry energy at saturation point. We have investigated the isoscalar giant monopole resonance (ISGMR) and the isoscalar giant dipole resonance (ISGDR) in Sn isotopes, using inelastic $\alpha$-particle of 400 MeV at extremely forward angles, including 0$^\circ$. The ISGMR and ISGDR strength distributions have been extracted from the background-free inelastic scattering spectra by using multipole-decomposition analysis. The implications of these results on the symmetry energy term will be discussed.