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Deformation and weak decay of Lambda hypernuclei

We use the self-consistent mean-field theory to discuss the ground state and decay properties of $Λ$ hypernuclei. We first discuss the deformation of $Λ$ hypernuclei using the relativistic mean-field (RMF) approach. We show that, although most of hypernuclei have a similar deformation parameter to the core nucleus, the shape of $^{28}$Si is drastically altered, from oblately deformed to spherical, if a $Λ$ particle is added to this nucleus. We then discuss the pionic weak decay of neutron-rich $Λ$ hypernuclei using the Skyrme Hartree-Fock + BCS method. We show that, for a given isotope chain, the decay rate increases as a function of mass number, due to the strong neutron-proton interaction.