On the role of ground state correlations in hypernuclear non-mesonic weak decay


The contribution of ground state correlations (GSC) to the non--mesonic weak decay of Ξ›12^{12}_\LambdaC and other medium to heavy hypernuclei is studied within a nuclear matter formalism implemented in a local density approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one-- and two--nucleon induced decays. Together with fermion antisymmetrization, GSC turn out to be important for an accurate determination of the decay widths. Besides opening the two--nucleon stimulated decay channels, for Ξ›12^{12}_\LambdaC GSC are responsible for 14% of the rate Ξ“1\Gamma_1 while increasing the Ξ“n/Ξ“p\Gamma_{n}/\Gamma_{p} ratio by 4%. Our final results for Ξ›12^{12}_\LambdaC are: Ξ“NM=0.98\Gamma_{\rm NM}=0.98, Ξ“n/Ξ“p=0.34\Gamma_{n}/\Gamma_{p}=0.34 and Ξ“2/Ξ“NM=0.26\Gamma_2/\Gamma_{\rm NM}=0.26. The saturation property of Ξ“NM\Gamma_{\rm NM} with increasing hypernuclear mass number is clearly observed. The agreement with data of our predictions for Ξ“NM\Gamma_{\rm NM}, Ξ“n/Ξ“p\Gamma_n/\Gamma_p and Ξ“2\Gamma_2 is rather good.Comment: 32 pages, 9 figure

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