A Study of Multi-Λ Hypernuclei Within Spherical Relativistic Mean-Field Approach

Abstract

Abstract. This research article is a follow up of earlier work by M. Ikram et al., reported in International Journal of Modern Physics E 25, 1650103 (2016) wherein we searched for Λ magic numbers in experimentally confirmed doubly magic nucleonic cores in light to heavy mass region (ie.16 O − 208 P b) by injecting Λ's into them. In present manuscript, working within the state-of-art relativistic mean field theory with inclusion of ΛN and ΛΛ interaction in addition to nucleon-meson NL3* effective force, we extend the search of lambda magic numbers in multi-Λ hypernuclei using the predicted doubly magic nucleonic cores 292 120, 304 120, 360 132, 370 132, 336 138, 396 138 of elusive superheavy mass regime. In analogy to well established signatures of magicity in conventional nuclear theory, the prediction of hypernuclear magicity are made on the basis of one-, two-Λ separation energy (SΛ, S2Λ) and two lambda shell gaps (δ2Λ) in multi-Λ hypernuclei. The calculations suggest that the Λ numbers 92, 106, 126, 138, 184, 198, 240, and 258 might be the Λ shell closures after introducing the Λ's in elusive superheavy nucleonic cores. The appearance of new lambda shell closures other than the nucleonic ones predicted by various relativistic and non-relativistic theoretical investigations can be attributed to the relatively weak strength of spin-orbit coupling in hypernuclei compared to normal nuclei. Further, the predictions made in multi-Λ hypernuclei under study resembles quite closely with the magic numbers in conventional nuclear theory suggested by various relativistic and non-relativistic theoretical models. Moreover, in support of Λ shell closure the investigation of Λ pairing energy and effective Λ pairing gap has been made. We noticed a very close agreement of the predicted Λ shell closures with the survey made on the pretext of SΛ, S2Λ and δ2Λ except for the appearance of magic numbers corresponding to Λ = 156 which manifest in Λ effective pairing gap and pairing energy. Also, lambda single-particle spectrum is analyzed to mark the energy shell gap for further strengthening the predictions made on the basis of separation energies and shell gaps. Lambda and nucleon spin-orbit interactions are analyzed to confirm the reduction in magnitude of Λ spin-orbit interaction compared to the nucleonic case, however interaction profile is similar in both the cases. Lambda and nucleon density distributions have been investigated to reveal the impurity effect of Λ hyperons which make the depression of central density of the core of superheavy doubly magic nuclei. Lambda skin structure is also seen.

Prediction of unknown nuclear stability by Bayesian deep neural network

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