Deformation of Lambda hypernuclei

We study the deformation property of $\mathrm{\Lambda }$ hypernuclei using the relativistic mean field (RMF) method. We find that ${}_{\mathrm{\Lambda }}^{29}$Si and ${}_{\mathrm{\Lambda }}^{13}$C hypernuclei have spherical shape as a consequence of the additional $\mathrm{\Lambda }$ particle, whereas the corresponding core nuclei, ${}^{28}$Si and ${}^{12}$C, are oblately deformed. Most of other hypernuclei have a similar deformation parameter to the core nucleus, in accordance with the previous study with the non-relativistic Skyrme-Hartree-Fock method. We discuss the sensitivity of our results to the choice of pairing interaction and to the parameter set of the RMF Lagrangian.