Ground state normalization in the nonmesonic weak decay of 12ΛC hypernucleus 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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“…[15], which however was based on a rather simplistic analysis regarding a supposed phase space argument allowing a uniform sharing of the decay Q-value among the two or three final nucleons in one-or two-nucleon induced decays. Such analysis provided an indication for a ratio Γ 2 /Γ 1 ≃ 0.7 for 12 Λ C, while values scattered in the interval 0.2-0.5 were obtained theoretically [17][18][19][20][21][22]. Another experiment [16], performed at BNL, obtained an upper limit for 4 Λ He, Γ 2 /Γ 1 < 0.32 (95% CL), which seems to be incompatible with the indication of Ref.…”

mentioning

confidence: 87%

Exchange terms in the two-nucleon induced non-mesonic weak decay of Λ-hypernuclei

Bauer

Garbarino

2009

Nuclear Physics A

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The contribution of Pauli exchange terms to the two-nucleon induced non-mesonic weak decay of 12 Λ C hypernuclei, ΛN N → nN N (N = n or p), is studied within a nuclear matter formalism implemented in a local density approximation. We have adopted 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. The introduction of exchange terms turns out to reduce the two-nucleon induced non-mesonic rate by 18% and, jointly with an increase in the one-nucleon induced rate by the same magnitude, reveals to be significant for an accurate determination of the full set of hypernuclear non-mesonic decay widths in theoretical and experimental analyses. Hypernuclei, bound systems of neutrons, protons and hyperons, embody an important source of information able to match nuclear and particle physics. On the one hand, studies on the production mechanisms and the structure of hypernuclei [1] are of interest since they provide indications on the hyperonnucleon and hyperon-hyperon strong interactions which cannot be determined with precision from scattering experiments (such experiments are very challenging due to the very short hyperon lifetimes). Hypernuclear weak decay is on the other hand the only available tool to acquire knowledge on the baryon-baryon strangeness-changing interactions [2-5]. The above subjects, which presuppose the solution of complex many-body problems, are in turn crucially related to the renormalization of hyperons and mesons properties in

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“…At variance, the emission of three nucleons can be only achieved when V ΛN →N N acts over a GSC. It is therefore convenient to introduce the following hypernuclear ground state wavefunction [18]: where | is the uncorrelated core ground state wave-function, i.e., the Hartree-Fock vacuum, while the second term in the rhs represents 2p2h correlations and contains both direct (D) and exchange (E) matrix elements of the nuclear residual interaction V N N . Besides, |p Λ is the normalized state of the Λ, the particle and hole energies are denoted by ε i and:…”

Section: Many-body Terms In the Non-mesonic Decay Ratesmentioning

confidence: 99%