Two nucleon induced hypernuclear weak decay within a nuclear matter formalism

The FINUDA experiment has recently completed an extensive study of the weak decay of p-shell Λ-hypernuclei including both mesonic and non-mesonic modes. Charged mesonic decay rates have been determined based on the analysis of π − kinetic energy spectra, never measured before. The study of proton spectra from non-mesonic weak decay for p-shell hypernuclei, both single and in coincidence with a neutron, has triggered the investigation of the two-nucleon induced ΛN N → nN N decay channel: its weight has been evaluated to be Γ 2 /Γ NM = 0.21 ± 0.07 stat +0.03 sys −0.02 sys . Finally, a direct experimental evidence of the occurrence of the weak reaction Λnp → nnp in nuclei is presented for the first time. Three events have been found which can be attributed to 7 Λ Li and 9 Λ Be two-nucleon induced non-mesonic weak decay; the kinematical analysis is discussed here.

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“…This value is in agreement with the theoretical predictions [39,[41][42][43][44][45][46] and the latest KEK experimental results of Ref. [48].…”

Section: Proton Spectra From Nmwd and Determination Of γsupporting

confidence: 92%

“…All charge channels of the two-nucleon stimulated decay, Λnn → nnn, Λnp → nnp and Λpp → npp, are included in the diagrammatic microscopic approach of Refs. [39,[44][45][46]. In particular, Pauli exchange and ground state correlations were also studied [39,46].…”

Section: Proton Spectra From Nmwd and Determination Of γmentioning

confidence: 99%

Hypernuclear weak decay studies with FINUDA

et al. 2012

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“…The local density approximation (LDA) is employed to extend the calculation to finite nuclei. This approach was previously established [19,20] to evaluate the non-mesonic decay widths of 12 Λ C. There is a major value of this model which by itself adds sufficient novelty to the present work with respect to previous analyses [14,15] of the nucleon spectra from hypernuclear nonmesonic decay. We must indeed emphasize that the present approach is more microscopic (i.e., less phenomenological) than the previous ones.…”

Section: Models a Weak Decaymentioning

confidence: 90%

“…Indeed, the lately extracted Γ n /Γ p values [14,15] turned out to be in agreement with the previous, pure theoretical estimates of Refs. [16][17][18][19][20] obtained by using one-meson-exchange potentials to describe the one-nucleon induced, ΛN → nN weak transitions.…”

Section: Introductionmentioning

confidence: 99%

“…With the purpose of making the extraction of Γ n /Γ p less model dependent, in the present paper we make use of an alternative framework for hypernuclear decay: it consists of a nuclear matter formalism [19,20] extended to finite nuclei via the local density approximation, with the same weak OME transition potential (containing π, ρ, K, K * , ω and η exchange) of Ref. [17], in addition to the Monte Carlo intranuclear cascade code of Ref.…”

mentioning

confidence: 99%

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Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

et al. 2010

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Recent progress has been experienced in the field of hypernuclear weak decay, especially concerning the ratio of the neutron-to proton-induced Λ nonmesonic decay rates, Γ n /Γ p . Theoretical analyses of nucleon coincidence data have been performed in a finite nucleus framework. They led to the extraction of Γ n /Γ p values in agreement with pure theoretical estimates, thus providing an evidence for the solution of a longstanding puzzle. Here we present an alternative approach to the problem, based on a nuclear matter formalism extended to finite nuclei via the local density approximation. The work is motivated by the exigence to make the determination of Γ n /Γ p from data less model dependent. One-meson-exchange potentials are used for describing both the oneand two-nucleon induced decays, ΛN → nN and ΛN N → nN N . For the latter, treated within a microscopic approach, the channels Λnn → nnn and Λpp → npp are included in addition to the mode Λnp → nnp already considered, in a phenomenological way, in previous studies. The propagation of the final nucleons in the residual nucleus is simulated by an intranuclear cascade code. We evaluate single and double coincidence nucleon spectra for the nonmesonic decay of 12 Λ C. Through the comparison of our predictions with KEK coincidence data we determine Γ n /Γ p = 0.43 ± 0.10 for this hypernucleus, confirming previous finite nucleus analyses. The use of a high nucleon kinetic energy detection threshold such as 60 MeV makes the contribution of twonucleon induced channels quite small, but final state interaction effects are still important when extracting Γ n /Γ p from measured single nucleon distributions. Coincidence spectra suffer less from these effects even for a moderate detection threshold such as 30 MeV. In any case, final state interactions have to be considered for meaningful determinations of Γ n /Γ p . 21.80.+a, 13.30.Eg, 13.75.Ev

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Weak Decays of Hypernuclei

Parreño

Lecture Notes in Physics

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Two nucleon induced hypernuclear weak decay within a nuclear matter formalism

Cited by 24 publications

References 49 publications

Hypernuclear weak decay studies with FINUDA

Hypernuclear weak decay studies with FINUDA

Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

Weak Decays of Hypernuclei

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