Following the many successful implementations of effective universal configuration-interaction Hamiltonians, we endeavored to produce a universal $fp$ shell interaction tailored for the calcium isotopes, which we call UFP-CA. Starting from a state-of-the-art in-medium similarity renormalization group (IMSRG) interaction, linear combinations of Hamiltonian parameters that define the natural basis of the parameter space are constrained by the latest experimental data for the neutron-rich calcium isotopes. We show that this data-driven method for improving the Hamiltonian provides an excellent description of the known binding energies and spectra for the calcium isotopes within the $fp$ model space. This together with comparisons to results from energy-density functional models leads us to conclude that ${}^{60}\mathrm{Ca}$ is doubly magic at a similar level to ${}^{68}\mathrm{Ni}$. Several predictions are presented for unobserved low-lying excited states in ${}^{55-59}\mathrm{Ca}$ that will be accessible to future experiments.

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• Nuclear forces
• Nuclear structure & decays
• 59 ≤ A ≤ 89
• Nuclear density functional theory