Two-nucleon induced Λ decay in nuclei

Alberico, W. M.; Pace, A. De; Ericson, M.; Molinari, A.

doi:10.1016/0370-2693(91)90663-b

Cited by 97 publications

(75 citation statements)

References 22 publications

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“…This suggests that some others relevant physical ingredients are still missing. In this sense, our nuclear matter formalism is particularly suitable for: 1) analyzing the RPA correlations, and 2) the inclusion of the ΛNN → NNN decay [12][13][14][15].…”

Section: Discussionmentioning

confidence: 99%

Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Bauer

Krmpoti

2003

Nuclear Physics A

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The nonmesonic weak decay of Λ hypernuclei using nonrelativistic nuclear matter is studied. As the basic building block we use the Polarization Propagator Method developed by Oset and Salcedo. It is shown that the exact calculation of exchange terms is required. Using the Local Density Approximation we evaluate the nonmesonic decay width for 12 Λ C and compare the result with a finite nucleus calculation, obtaining a qualitative agreement.PACS number: 21.80.+a, 25.80.Pw.

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Section: Discussionmentioning

confidence: 99%

Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Bauer

Krmpoti

2003

Nuclear Physics A

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“…The relevance of the two-nucleon induced channel, ΛNN → NNN, in the decay of hypernuclei was first pointed out by Alberico et al [110]. This transition can be viewed as coming from the absorption of a virtual pion emitted in the weak vertex by two strongly correlated nucleons, as depicted schematically in fig. 14.…”

Section: Two-nucleon Induced Decaymentioning

confidence: 99%

“…An interesting point raised in ref. [110] was that this channel affects the emission of neutrons and could have some relevance in the experimental determination of the ratio Γ n /Γ p . Since pions are absorbed mainly by neutron-proton pairs, the 2N-induced decay proceeds basically through the mode Λnp → nnp, emitting twice as many neutrons than protons.…”

Section: Two-nucleon Induced Decaymentioning

confidence: 99%

Weak decay of Λ hypernuclei

Oset

1998

Progress in Particle and Nuclear Physics

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We review recent developments concerning the weak decay of Λ hypernuclei. New studies covering the mesonic decay channel as well as recent models for the non-mesonic one are discussed and compared with experimental data. The puzzle of the neutron-to proton-induced decay ratio, Γ n /Γ p , is addressed in connection to the two-nucleon induced decay channel and proposals for more efficient experimental analyses of this ratio are made. : 21.80.+a, 13.30.Eg, 25.80.Pw, 13.75.Ev Keywords: Λ hypernuclei, Mesonic decay of hypernuclei, Non-mesonic decay of hypernuclei, Weak interaction, ∆I = 1/2 rule. PACS

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“…We also have taken the data at face value and have not applied any corrections due to, e.g., the two-nucleon-induced mechanism, which has been estimated to amount up to 25% of the total decay rate for p-shell hypernuclei [28,29]. Ideally, exclusive experiments would separate this mechanism from the measured total decay rate, permitting a fit to observables that are not contaminated with multinucleon effects.…”

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confidence: 99%

ΛN→NNweak interaction in effective-field theory

2004

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The nonleptonic weak ͉⌬S͉ =1 ⌳N interaction, responsible for the dominant nonmesonic decay of all but the lightest hypernuclei, is studied in the framework of an effective-field theory. The long-range physics is described through tree-level exchange of the SU(3) Goldstone bosons, while the short-range potential is parametrized in terms of the lowest-order contact terms. We obtain reasonable fits to available weak hypernuclear decay rates and quote the values for the parity-violating asymmetry as predicted by the present effective-field theory. For the past 50 years, ⌳ hypernuclei, systems of one or more ⌳ hyperons bound to a core nucleus, have been used to extend our knowledge of both the strong and the weak baryon-baryon interaction from the NN case into the SU(3) sector. The nonmesonic hypernuclear weak decay, facilitated via the ͉⌬S͉ = 1 four-fermion interaction, thus complements the weak ⌬S =0 NN case, which allows the study of only the parity-violating amplitudes.In analogy to NN phenomenology, the nonmesonic hypernuclear decay has traditionally been modeled using a mesonexchange approach [1]. The long-range part of the interaction is naturally explained by one-pion exchange, which could approximately reproduce the total (one-nucleoninduced) nonmesonic decay rate, ⌳N → NN, but not the partial rates, the proton-induced ⌳p → np rate ⌫ p , and the neutron-induced ⌳n → nn rate ⌫ n [2]. Due to the ⌳N mass difference, the process ⌳N → NN produces nucleons with momenta around Ϸ420 MeV, suggesting that the short-range part of the interaction cannot be neglected. These contributions have been described either through the exchange of vector mesons [3,4], whose production thresholds are too high for the free ⌳ decay, or through direct quark exchange [5].In contrast to previous theoretical studies, we present an exploratory study in order to determine the possible efficacy of the use of effective-field theory (EFT) methods in hypernuclear decay. Studies in this direction have already begun in Ref. [6], where a Fermi ͑V-A͒ interaction was added to the one-pion-exchange (OPE) mechanism to describe the weak ⌳N → NN transition. The present approach is motivated by the remarkable success of EFT techniques based on chiral expansions in the (nonstrange) SU(2) sector [7-10], which suggests its extension to the SU(3) realm, even though stability of the chiral expansion is less clear for the SU(3) sector, due to the significant degree of SU(3) symmetry breaking. A well-known example of the problems facing the SU(3) chiral perturbation theory has been the prediction [11][12][13][14] The EFT approach is based on the existence of wellseparated scales in the physical process under study. Formally, the high-momentum (short-distance) modes in the four-baryon interaction Lagrangian are replaced by contact operators, compatible with the underlying physical symmetries, of increasing dimension. Built in such a way, the Lagrangian will contain an infinite number of terms, and a consistent power-counting scheme is needed in order to trunca...

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Two-nucleon induced Λ decay in nuclei

Cited by 97 publications

References 22 publications

Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Weak decay of Λ hypernuclei

ΛN→NNweak interaction in effective-field theory

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