Compression-mode resonances in the calcium isotopes and implications for $K_\tau$

Recent data on isoscalar giant monopole resonance (ISGMR) in the calcium isotopes \nuc{40,44,48}{Ca} have suggested that $K_\tau$, the asymmetry term in the nuclear incompressibility, has a positive value. A value of $K_\tau > 0$ is entirely incompatible with present theoretical frameworks and, if correct, would have far-reaching implications on our understanding of myriad nuclear and astrophysical phenomena. This paper presents results of an independent ISGMR measurement with the \nuc{40,42,44,48}{Ca}($\alpha,\alpha^\prime$) reaction at $E_\alpha = 386$ MeV. These results conclusively discount the possibility of a positive value for $K_\tau$, and are consistent with the previously-obtained values for this quantity.