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Nucleon-Nucleon Coincidence Spectra in the Non-Mesonic Weak Decay of Lambda-Hypernuclei and the n/p Puzzle

G. Garbarino·A. Parreno·A. Ramos
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Abstract

The main open problem in the physics of Lambda-hypernuclei is the lack of a sound theoretical interpretation of the large experimental values for the ratio G_n/G_p. To approach the problem, we have incorporated a Lambda N-> nN one-meson-exchange model in an intranuclear cascade code for a finite nucleus calculation of the nucleon-nucleon (angular and energy) coincidence distributions in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C hypernuclei. The two-nucleon induced decay mechanism, Lambda np-> nnp, has been taken into account by means of the polarization propagator formalism in local density approximation. With respect to single nucleon spectra studies, the treatment of two-nucleon correlations allow a cleaner and more direct determination, from data, of G_n/G_p. Our results agree with the preliminary coincidence data of KEK-E462 for 5_Lambda-He. This allows us to conclude that G_n/G_p for 5_Lambda-He should be close to 0.46, the value predicted by our one-meson-exchange model for this hypernucleus. Unfortunately, to disentangle one- and two-body induced decay channels from experimental non-mesonic decay events, three-nucleon coincidences should be measured.

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G. Garbarino, A. Parreno, A. Ramos. 2003-01-17. Nucleon-Nucleon Coincidence Spectra in the Non-Mesonic Weak Decay of Lambda-Hypernuclei and the n/p Puzzle. https://doi.org/10.1103/physrevlett.91.112501

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