$\sigma$ meson exchange effect on nonmesonic hypernuclear weak decay observables

Abstract

We analyze the influence of $\sigma$ meson exchange on the main nonmesonic hypernuclear weak decay observables: the total rate, ${\Gamma }_{NM}$, the neutron-to-proton branching ratio, ${\Gamma }_{n/p}$, and the proton asymmetry parameter, $a_{\Lambda }$. The $\sigma$ meson exchange is added to the standard strangeness-changing weak $\Lambda N\to NN$ transition potential, which includes the exchange of the complete pseudoscalar and vector mesons octet ($\pi$, $\eta$, $K$, $\rho$, $\omega$, $K^{\ast }$). Using a shell model formalism, the $\sigma$ meson weak coupling constants are adjusted to reproduce the recent ${\Gamma }_{NM}$ and ${\Gamma }_{n/p}$ experimental data for ${}_{\Lambda }^{5}He$. Numerical results for the remaining observables of ${}_{\Lambda }^{5}He$ and all the observables of ${}_{\Lambda }^{12}C$ decays are presented. They clearly show that the addition of the $\sigma$ meson, in spite of improving some observables values, is not enough to reproduce simultaneously all the measurements, and the puzzle posed by the experimental data remains unexplained.

4 pages, 1 figure. Submitted for publication in Phys. Rev

References in corpus (13)

• Weak Decay of Lambda Hypernuclei
• Meson exchange in the weak decay of Lambda hypernuclei and the Gamma_n/Gamma_p ratio
• Final State Interactions in Hypernuclear Decay
• Towards the solution of the Gn/Gp Puzzle in the Non-Mesonic Weak Decay of Lambda-Hypernuclei
• Nonmesonic weak decay of light hypernuclei with coherent $\Sigma$ mixing
• Sigma Exchange in the Nonmesonic Decays of Light Hypernuclei and Violation of the Delta I=1/2 Rule
• Erratum: Neutron and proton spectra from the decay of $\Lambda$ hypernuclei [Phys. Rev. C55, 735 (1997)]
• $\Lambda N\to NN$ weak interaction in effective field theory
• Asymmetries in the Non-Mesonic Weak Decay of Polarized Lambda-Hypernuclei
• Kinematical and nonlocality effects on the nonmesonic weak hypernuclear decay
• Asymmetry parameter for nonmesonic hypernuclear decay
• Proton asymmetry in non-mesonic weak decay of light hypernuclei
• Non-Mesonic Weak Decay of Lambda-hypernuclei: a new determination of the Gn/Gp ratio

Cited by in corpus (6)

• Strangeness in nuclear physics
• Strangeness nuclear physics: a critical review on selected topics
• Two-pion-exchange in the non-mesonic weak decay of $\Lambda$-hypernuclei
• Single and double coincidence nucleon spectra in the weak decay of Lambda hypernuclei
• Current constraints on the EFT for the ΛN --> N N transition
• Microscopic approach to the proton asymmetry in the non-mesonic weak decay of Lambda-hypernuclei