The non-mesonic decay of helium hypernuclei.



Publisher: Presses académiques européennes in Bruxelles

Written in English
Published: Pages: 11 Downloads: 773
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Subjects:

  • Helium -- Isotopes -- Decay.

Edition Notes

Bibliography: leaves 7-8.

Statement[By] G(hislaine) Coremans [and others]
SeriesUniversité libre de Bruxelles. Faculté des sciences appliquées. Institut de physique. Service de physique nucléaire. Physique des particules élémentaires. Bulletin no. 35
ContributionsCoremans, Ghislaine.
Classifications
LC ClassificationsQC770.B7 A27 no. 35
The Physical Object
Pagination11 l.
Number of Pages11
ID Numbers
Open LibraryOL5001737M
LC Control Number76508542

nucleon spectra for the non–mesonic decay of 5 ΛHe and 12 Λ C hypernuclei was presented in [20,21].A one–meson–exchange (OME) potential was used forthe ΛN→ nNtransition in a finite nucleus framework. The model adopted for the two–nucleon induced decay channel is described in . The high intensity pion beams by the slow beam extraction will be used. Our subjects are a copious production of the neutron-rich hypernuclei by the double-charge exchange (DCX) reactions (E10) and a detail study on the non-mesonic weak decay in the A=4 hypernuclei (E22). E Study of Neutron-Rich Lambda Hypernuclei. Get this from a library! Hypernuclear and Strange Particle Physics.. [J Pochodzalla; Thomas Walcher] -- This volume contains the proceedings of the IX International Conference on Hypernuclear and Strange Particle Physics (HYP ). This conference series, started in , is devoted to the progress of. The weak decay of helium hypernuclei Technical Report Athanas, M.J. A [Lambda] hyperon replaces a neutron in a nucleus to form a hypernucleus via the [sup A]X(K[sup [minus]], [pi][sup [minus]]) [sub [Lambda]][sup A]X reaction at MeV/c (Brookhaven Experiment ).

Decay asymmetry in non-mesonic weak decay of light Λ-hypernuclei. (et al.) Preview Buy Chap19 € The quenching of nucleon yields in the nonmesonic weak decay of Λ-hypernuclei and the three-body weak decay process. *immediately available upon purchase as print book shipments may be delayed due to the COVID crisis. ebook. Non-mesonic weak decays of light hypernuclei in the direct quark and the one-pion exchange mechanisms T. Inoue, M. Oka, T. Motoba and K. Itonaga 1 Apr | Nuclear Physics A, Vol. , No. 2. The ground state of heliumLambda, for example, must resemble helium-4 more than it does helium-5 or lithium-5 and must be stable, apart from the eventual weak decay of the Lambda. Sigma hypernuclei have been sought, as have doubly-strange nuclei containing Cascade baryons. Hypernuclei can be made by a nucleus capturing a Lambda or K meson.   The weak decay of hyperons may occur, in principle, with isospin change ΔI = 1/2 or 3/2. However, the values of the experimental decay branching ratios imply a dominance of a factor 20 of ΔI = 1/2 over ΔI = 3/2. Nevertheless, experimental analysis of some non-mesonic decay channels seems to suggest a strong violation of this rule.

Charge Symmetry Breaking in Light Hypernuclei Achenbach P. (Mainz University, Germany) A1 Collaboration At the Mainz Microtron MAMI the high-resolution spectroscopy of decay-pions in strangeness electro-production is used to extract the Λ hyperon ground state bind-ing energy in 4 Λ H [1]. This binding energy is used together with the 4 Λ He. ΛHe hypernuclei, a few 5 ΛHe → d+t decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: ( ±) ×10−3. Key words: Light Hypernuclei; Non Mesonic Weak Decay PACS: +a, Pw 1 Introduction Two weak decay modes ofΛHypernuclei areknown, mesonic andNon-Mesonic (NM). 3 H decay lifetime t5~ 1 ! @11#~neglecting the non-mesonic piece!, using the factor 3/2 of Eq. ~3! from isospin and the ratio R ~see the Introduction!. The decay rates and lifetimes for both mesons are given in Table I. Let us now ask more detailed questions in relation to that 3He channel. For the free L decay into p1p2. Non-mesonic decay − Λ K− +AZ → AZ +π pairs production and detection of hypernuclei. Res. at 80 MeV, time resolution ps FWHM) • Helium gas chamber:multiple scattering reduction.

The non-mesonic decay of helium hypernuclei. Download PDF EPUB FB2

The analysis is reported of a sample of hypernuclei decaying non-mesonically with the emission of one or two charged particles which were obtained from K − meson captures at rest in nuclear emulsion. Making use of the decay parameters established for the 4 Λ He hypernucleus from observations in a helium bubble chamber, a value of Q −, the ratio of non-mesonic to π − mesonic Cited by: The analysis is reported of a sample of hypernuclei decaying non-mesonically with the emission of one or two charged particles which were obtained from K - meson captures at rest in nuclear emulsion.

Making use of the decay parameters established for the 4 Λ He hypernucleus from observations in a helium bubble chamber, a value of Q- the ratio of non-mesonic to π. The non-mesonic decay modes of Λ hypernuclei are examined. The one-nucleon induced decay (ΛN → NN) is studied in a shell-model framework using a meson Author: A.

Ramos, C. Bennhold, E. Oset, L.L. Salcedo, M.J. Vicente-Vacas. DI-fusion, le Dépôt institutionnel numérique de l'ULB, est l'outil de référencementde la production scientifique de l'ULB.L'interface de recherche DI-fusion permet de consulter les publications des chercheurs de l'ULB et les thèses qui y ont été by:   For the first time the hypothetical 3 He-η bound state was searched for in non-mesonic p d → 3 He 2 γ and p d → 3 He 6 γ decays.

For the purpose of the experimental data interpretation, a new theoretical model for the η-mesic helium was developed, according to which the mesic nucleus decays without η meson by: 2. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Theoretical descriptions of the non–mesonic weak decay of Λ–hypernuclei are unable to reproduce the experimental values of the ratio Γn/Γp ≡ Γ(Λn → nn)/Γ(Λp → np).

In this contribution we discuss a new approach to this problem. We have incorporated a one–meson–exchange model for the ΛN → nN. We review the current status of studies of weak decays of Λ-hypernuclei.

Both experimental and theoretical aspects are reviewed, with emphasis on the weak non-mesonic decays. Experimental results obtained during the last thirty years are described and discussed in detail. We present an evaluation of the non-mesonic decay widths for Λ-hypernuclei (ΛN→ NN, ΛNN→ NNN) within the framework of the polarization propagator method.

The full Λ self-energy is evaluated microscopically in nuclear matter by using the functional approach, which supplies a theoretically well grounded approximation scheme for the classification of the relevant diagrams, according to.

Weak non-mesonic decay of Hypernuclei W.M. Alberico∗ Dipartimento di Fisica Teorica and INFN, via P. Giuria 1, I Torino, Italy February 8, Abstract We review the mechanism of weak decay of hypernuclei, with em-phasis on the non-mesonic decay channels. Various theoretical ap. Very sensitive studies hypernuclei are now possible at Brookhaven.

The p{lambda} {yields} s{lambda} gamma ray transition in the hypernucleus {lambda}{sup 13}C has been observed in an experiment using sodium iodide detectors. An experiment to study the formation and decay of {lambda}{lambda} hypernuclei is being prepared.

and branching ratios of mesonic as well as nonmesonic decay channels of 12 Λ C, 11 Λ B and the different helium hypernuclei [7,8]. The group at KEK used the (π+,K+) production reaction to not only measure total and partial decay rates [9], but also to use the induced polarization in Notably, the two–body component of the non–mesonic decay rates has not been measured yet, due to the too low counting rates expected for a coincidence experiment.

For the asymmetric non–mesonic decay of polarized hypernuclei the situation is even more puzzling. Indeed, strong inconsistencies appear already among data. scattering. The mesonic decay of light hypernuclei has provided evidence of the strong repulsion of the ΛNinteraction at short distances, a property that follows naturally from available quark models of the strong YNinteraction.

The non-mesonic decay mode (ΛN → NN) has received much attention and 3. We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus.

The hypernuclei were created using a MeV/c momentum K. Making use of the decay parameters established for the 4ΛHe hypernucleus from observations in a helium bubble chamber, a value of Q−, the ratio of non-mesonic to π− mesonic decays, for λ5He.

Abstract. The proton decay asymmetry, α p NM, of the polarized Λ-hypernuclei, Λ 5 He, Λ 12 C and Λ 11 B, has been investigated to understand the reaction mechanism of the non-mesonic weak-decay process. These Λ-hypernuclei were produced in the highest statistics ever via the (π +, K +) reaction at GeV/c by using the SKS spectrometer at KEK 12 GeV PS.

1 Hyperons and hypernuclei Introduction Hyperons (, Ω) have lifetimes of the order of 10 −10 sec (apart from the 0, which decays into γ).They decay weakly, with a mean free path ˇ c˝= O(10 cm).

Ahypernucleus is a boundsystem of neutrons, protonsand oneormore hyperons. The nonmesonic weak decay spectra of light hypernuclei have been evaluated in a systematic way. As theoretical framework we adopt the independent particle shell.

By measuring the relative decay widths ({Gamma}{sub n}/{Gamma}{sub p}) in the full set of s-shell hypernuclei, a sensitive test of the {Delta}I = 1/2 rule, and the determination of its applicability to non-mesonic decays can be made. In addition, information about the spin-isospin dependence of the weak decay process can be extracted.

We have studied the mesonic and non-mesonic decay width of Λ-hypernuclei by performing calculations in nuclear matter and using the local-density prescription to apply the results to finite nuclei. We review recent developments concerning the weak decay of Lambda hypernuclei.

New studies covering the mesonic decay channel as well as recent models for the. @article{osti_, title = {Polarization effects in decays of hypernuclei}, author = {Lyul'ka, V A}, abstractNote = {The polarization of the protons in the hypernucleus decay /sup 5/He/./>./sup 4/He+p+./sup -/ is calculated.

It is shown that the final-state resonance interaction in the p-/sup 4/He system essentially determines the angular dependence of the proton. In Sect. 2 I discuss the possible modes for a hyperon to decay, the mesonic channel (Λ → πN) and the non-mesonic channel (Λ N ⇒ N N), which constitutes the dominant mode when the decay.

@article{osti_, title = {Weak decay of hypernuclei}, author = {Grace, R}, abstractNote = {The Moby Dick spectrometer (at BNL) in coincidence with a range spectrometer and a TOF neutron detector will be used to study the weak decay modes of /sup 12/C.

The Moby Dick spectrometer will be used to reconstruct and tag events in which specific hypernuclear states are formed in the reaction K.

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 Lambda NN.

The isotopic composition refers to that in air. Helium-2 (diproton) Helium-2 or 2 He is an extremely unstable isotope of helium. Its nucleus, a diproton, consists of two protons with no ing to theoretical calculations, it would have been much more stable (although still undergoing β + decay to deuterium) if the strong force had been 2% greater.

A dedicated and systematic experimental study made possible the achievement of some new results about the non-mesonic weak decay of hypernuclei.

Among others, the first determination of the one-proton induced non-mesonic weak decay width for several p -shell Λ-hypernuclei contributed in defining a coherent picture of the complete set of decay.

Hypernuclei were discovered in by M. Danysz and J. Pniewski in photographic emulsions that went with high altitude balloon flights. The weak decay of a Λ nucleon accounted for the abundant energy release in a secondary star, which is the signature of what was called a hyperfragment.

Many surprises were offered by hypernuclei through a large variety of experiments over a long period. Abstract. This paper summarizes the available information on S-shell hypernuclei, particularly with respect to their weak decays.

It is also pointed out that a measurement of the branching ratios in the non-mesonic weak decay of Λ 4 H is crucial in order to test the ΔI=1/2 rule in the strangeness changing non-leptonic weak decay process.

We emphasize that collectively, the S-shell. The quenching of nucleon yields in the nonmesonic weak decay of Λ-hypernuclei and the three-body weak decay process H.

Bhang, S. Ajimura, K. Aoki, A. Banu, T. Fukuda, O. Hashimoto et. Summary. The helium bubble chamber was exposed to a stopping K-beam and 4 He Λ hypernuclei, produced in the reaction K-+ 4 He→ →π-+ 4 He Λ, were probability forp-wave emission in the decay Λ 0 →n + π 0 was deduced to be p 0 2 (p 0 2 +s 0 2) = 0.l6±, from the ratio of the decay modes 4 He Λ → all π 0 and 4 He inΛ → all result is in good agreement.Recent measurements of the weak decay.

hypernuclei are reported and discussed in the context of the weak hyperon-baryon effective Hamiltonian.

The results are compared to predictions of both meson exchange and quark-quark weak interaction models. 14 refs., 4 figs., 2 tabs.The expected performances of the FINUDA experiment in hypernuclear decay measurements are presented.

Lifetimes and relevant observables of mesonic and non-mesonic decay of light and medium Λ-hypernuclei can be measured with good precision at the DAΦNE design luminosity.