Hypernuclear weak decay experiments at KEK: n–n and n–p coincidence measurement

Outa, H.; Ajimura, S.; Aoki, Katsumi; Banu, A.; Bhang, H.; Fukuda, T.; Hashimoto, Osamu; Hwang, J. I.; Kameoka, S.; Kang, B. H.; Kim, E.H.; Kim, J.H.; Kim, M.J.; Maruta, T.; Miura, Y.; Miyake, Yasuhiro; Nagae, T.; Nakamura, Makoto; Nakamura, S. N.; Noumi, H.; Okada, S.; Okayasu, Y.; Park, H.; Saha, Pranab; Sato, Y.; Sekimoto, M.; Takahashi, Toshiya; Tamura, H.; Tanida, K.; Toyoda, A.; Tsukada, K.; Watanabe, T.; Yim, H.

doi:10.1016/j.nuclphysa.2005.03.007

Cited by 31 publications

(25 citation statements)

References 13 publications

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“…However, hypernuclear systems decay, precisely due to the presence of surrounding nucleons, by means of single-nucleon-induced, 1N = N → NN, and multinucleon-induced decay mechanisms. Recently, the detection of two nucleons in coincidence in the final state [10][11][12] has allowed a more reliable extraction not only of the total nonmesonic decay rate, but also of the ratio between the neutron-induced process ( n → nn) and the proton-induced one ( p → np), n / p [13,14]. The analysis of the data points out that, in order to isolate the physical region where medium effects and multinucleon-induced processes are minimal, one needs to study the energy and angular correlated spectra for the particles detected in the final state, instead of looking at the absolute values for the partial and total decay rates.…”

Section: Meson Exchange Potentialmentioning

confidence: 99%

Constraints on effective field theory parameters for theΛN→NNtransition

2011

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The relation between the low-energy constants appearing in the effective field theory description of the N → NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.

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Section: Meson Exchange Potentialmentioning

confidence: 99%

Constraints on effective field theory parameters for theΛN→NNtransition

2011

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“…For a long time the large experimental value for the Γ n/p ratio (close to unity) remained unexplained. But, recent improved data tend to converge to ∼ = 0.5 [7][8][9][10], both for 5 Λ He (s-shell) and 12 Λ C (p-shell), indicating similarity in the transition mechanism.…”

Section: Introductionmentioning

confidence: 98%

“…This attribute of hypernuclei has motivated a recent proposal to produce neutron rich Λ-hypernuclei at the Japan Proton Accelerator Research Complex (J-PARC), including 9 Λ He [2] 1 . Important experimental efforts have been invested in hypernuclear weak physics during the last few years [5][6][7][8][9][10][11][12][13][14][15][16]. The correlative theoretical advances in our knowledge of the NMWD, have been also quite significant .…”

Section: Introductionmentioning

confidence: 99%

Relationships between nonmesonic weak decays in different hypernuclei

Krmpotić

2010

Phys. Rev. C

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Using as a tool the s-wave approximation (sWA), this work demonstrates that the nonmesonic weak decay transition rates Γn and Γp can be expressed in all hypernuclei up to 29 Λ Si (and very likely in heavier ones too) in the same way as in the s-shell hypernuclei, i.e., as a linear combination of only three elementary transition rates. This finding leads to the analytic prediction that, independently of the transition mechanism, all hypernuclei that are on the stability line (N = Z), i.e., 5 Λ He, 7 Λ Li, 9 Λ Be, 11 Λ B, 13 Λ C, 17 Λ O, 29 Λ Si, etc should roughly have the same ratio Γn/Γp, the magnitude of which rapidly increases when one approaches the neutron drip-line (N ≫ Z), and opposite happens when one goes toward the proton drip-line (N ≪ Z).

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“…25 On the other hand, the one-particle proton and neutron kinetic energy spectra in 4 Λ He measured at BNL 26 are accounted for reasonably well theoretically by considering only the 1N -NM decay mode. 8,9 The above mentioned experiments, together with several others performed during the last few decades, 23,[27][28][29][30][31][32][33][34][35] represent very important advances in our knowledge about NM decay. Explicitly, these advances are: 1) new high quality measurements of the number of single-nucleons N N , as a function of the one-nucleon energy E N , and 2) first measurements of the number of two-particle coincidences N nN , as a function of: i) the sum of the kinetic energies E nN ≡ E n + E N , ii) the opening angle θ nN , and iii) the center of mass (c.m.)…”

Section: Introductionmentioning

confidence: 99%

Nonmesonic weak decay dynamics from proton spectra of Λ-hypernuclei

Krmpotić

Conti

2014

Int. J. Mod. Phys. E

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A novel comparison between the data and the theory is proposed for the nonmesonic (NM) weak decay of hypernuclei. Instead of confronting the primary decay rates, as is usually done, we focus attention on the effective decay rates that are straightforwardly related with the number of emitted particles. Proton kinetic energy spectra of 5 Λ He, 7 Λ Li, 9 Λ Be, 11 Λ B, 12 Λ C, 13 Λ C, 15 Λ N and 16 Λ O, measured by FINUDA, are evaluated theoretically. The Independent Particle Shell Model (IPSM) is used as the nuclear structure framework, while the dynamics is described by the One-Meson-Exchange (OME) potential. Only for the 5 Λ He, 7 Λ Li, and 12 Λ C hypernuclei is it possible to make a comparison with the data, since for the rest there is no published experimental information on number of produced hypernuclei. Considering solely the one-nucleon-induced (1N -NM) decay channel, the theory reproduces correctly the shapes of all three spectra at medium and high energies (Ep > ∼ 40 MeV). Yet, it greatly overestimates their magnitudes, as well as the corresponding transition rates when the full OME (π + K + η + ρ + ω + K * ) model is used. The agreement is much improved when only the π + K mesons with soft dipole cutoff parameters participate in the decay process. We find that the IPSM is a fair first order approximation to disentangle the dynamics of the 1N -NM decay, the knowledge of which is indispensable to inquire about the baryon-baryon strangeness-flipping interaction. It is shown that the IPSM provides very useful insights regarding the determination the 2N -NM decay rate. In a new analysis of the FINUDA data, we derive two results for this quantity with one of them close to that obtained previously.

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Hypernuclear weak decay experiments at KEK: n–n and n–p coincidence measurement

Cited by 31 publications

References 13 publications

Constraints on effective field theory parameters for theΛN→NNtransition

Constraints on effective field theory parameters for theΛN→NNtransition

Relationships between nonmesonic weak decays in different hypernuclei

Nonmesonic weak decay dynamics from proton spectra of Λ-hypernuclei

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