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MECHANISMS OF THE NONMESONIC WEAK DECAY OF Λ HYPERNUCLEI AND THE THREE-BODY PROCESS
BHANG, H.,AJIMURA, S.,AOKI, K.,BANU, A.,FUKUDA, T.,HASHIMOTO, O.,HWANG, J. I.,KAMEOKA, S.,KANG, B. H.,KIM, E.,KIM, J. H.,KIM, M.,MARUTA, T.,MIURA, Y.,MIYAKE, Y.,NAGAE, T.,NAKAMURA, M.,NAKAMURA, S. N. World Scientific 2009 Modern Physics Letters A Vol.24 No.11
<P> The long standing Γn/Γp puzzle of NMWD has finally been solved recently. It appears that the reason behind the puzzle was the universal quenching of nucleon yields from the prediction of one-nucleon induced (1N-) NMWD. We have shown that the quenching of nucleon yields can be explained only when we include a fairly large contribution of the three-body process (Γ2N) in Γnm. </P>
Coincidence measurement of the nonmesonic weak decay of <sup>12</sup><sub><i>Λ</i></sub>C
Kim, M.J.,Ajimura, S.,Aoki, K.,Banu, A.,Bhang, H.,Fukuda, T.,Hashimoto, O.,Hwang, J.I.,Kameoka, S.,Kang, B.H.,Kim, E.H.,Kim, J.H.,Maruta, T.,Miura, Y.,Miyake, Y.,Nagae, T.,Nakamura, M.,Nakamura, S.N. Elsevier 2006 Physics letters: B Vol.641 No.1
<P><B>Abstract</B></P><P>We have measured the angular correlation of the pair nucleons <I>np</I> and <I>nn</I> emitted from the nonmesonic weak decay (NMWD) of <SUP>12</SUP><SUB><I>Λ</I></SUB>C produced via the (<SUP>π+</SUP>,<SUP>K+</SUP>) reaction in coincidence measurement. The Λp→np and Λn→nn modes were clearly identified by measuring the back-to-back correlation of the emitted nucleon pairs which is the characteristic of two-body kinematics. From the measured nucleon pair numbers <SUB>Nnn</SUB> and <SUB>Nnp</SUB>, the ratio <SUB>Γn</SUB>/<SUB>Γp</SUB> of the partial decay widths <SUB>Γn</SUB>(Λn→nn) and <SUB>Γp</SUB>(Λp→np) of <SUP>12</SUP><SUB><I>Λ</I></SUB>C was extracted to be 0.51±0.13(stat)±0.05(syst); this result is almost free from the ambiguity due to the nuclear final state interaction and 3-body decay process, which were inherent in the previous results. The obtained <SUB>Γn</SUB>/<SUB>Γp</SUB> ratio of <SUP>12</SUP><SUB><I>Λ</I></SUB>C (<I>p</I>-shell) is close to that of <SUP>5</SUP><SUB><I>Λ</I></SUB>He (<I>s</I>-shell). The results are consistent with those of recent theoretical calculations.</P>
Invariant Mass Spectroscopy for the Neutron Rich Nuclei
사토,추경호,방형찬,S. H. Choi,T. Nakamura,Y. Kondo,Y. Nakayama,N. Kobayashi,K. N. Tanaka,S. Deguchi,Y. Kawada,N. Tanaka,T. Sugimoto,T. Motobayashi,H. Sakurai,H. Otsu,N. Aoi,Y. Yanagisawa,S. Takeuchi,N. Fukuda 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The neutron-rich carbon isotopes ^(19,17)C and a boron isotope ^(14)B are investigated respectively via proton inelastic and charge-exchange reactions on a liquid hydrogen target at around 70 MeV/nucleon at RIKEN. The invariant mass method in inverse kinematics involving coincidence detection of a charged fragment and a neutron both emitted at forward angles is employed to map the energy spectrum above the neutron decay threshold. Several resonance structures are revealed in the invariant mass spectra, and the nature for some of them is discussed from comparisons of differential cross section data with predictions of microscopic DWBA calculations based on spsdpf shell model wave functions and a recent parametrization of semi-microscopic nucleon-nucleus optical model potential (JLMB). By extrapolating the (p,n) cross sections leading to the 1^+ state at 1.27 MeV in ^(141)B to zero momentum transfer the Gamow-Teller transition strength is deduced. The value is found to compare well with that reported in a β-delayed neutron emission study.
Proton-hole and core-excited states in the semi-magic nucleus 131In82
Taprogge, J.,Jungclaus, A.,Grawe, H.,Borzov, I. N.,Nishimura, S.,Doornenbal, P.,Lorusso, G.,Simpson, G. S.,Sö,derströ,m, P. -A.,Sumikama, T.,Xu, Z. Y.,Baba, H.,Browne, F.,Fukuda, N.,Gernhä Springer-Verlag 2016 The european physical journal. A, Hadrons and nucl Vol.52 No.11
<P>The decay of the N = 83 nucleus Cd-131 has been studied at the RIBF facility at the RIKEN Nishina Center. The main purpose of the study was to identify the position of the and proton-hole states and the energies of core-excited configurations in the semi-magic nucleus In-131. From the radiation emitted following the decay, a level scheme of In-131 was established and the feeding to each excited state determined. Similarities between the single-particle transitions observed in the decays of the N = 83 isotones In-132 and Cd-131 are discussed. Finally the excitation energies of several core-excited configurations in In-131 are compared to QRPA and shell-model calculations.</P>
The Weak Decay Widths of Λ Hypernuclei
H. Bhang,S. Ajimura,K. Aoki,A. Banu,T. Fukuda,O. Hashimoto,J. I. Hwang,S. Kameoka,B. H. Kang,E. Kim,김정호,T. Maruta,Y. Miura,Y. Miyake,T. Nagae,M. Nakamura,S. N. Nakamura,H. Noumi,S. Okada,Y. Okayasu,H. 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
We have measured both the mesonic and nonmesonic weak decay widths of ^(12)_ΛC. For the mesonic decay, we have improved the accuracy of Γ_π^0 so that it reduced the error of Γ_(nm) from ≥10% to ≤5%. For the nonmesonic decay, we have solved the long standing Γ_n/Γ_p puzzle by measuring the ratio 0.51 ± 0.14 in the exclusive measurement. At the same time we have measured the width of the 3-body nonmesonic decay Γ_(2N) = 0.27 ± 0.13 for the first time. Combining the accurate Γ_n/Γ_p ratio and the first measured value Γ_(2N), we have finally obtained the Γ_n and Γ_p themselves taking account of the 3-body process. We have measured all the weak decay widths of _(12)_ΛC so that it provides the first complete set of widths for the investigation of ΔS = 1 baryon-baryon weak interaction.
Concentration Quenching of Tb3+ Luminescence in TbxYb3-XAl5O12 Single Crystals
M.Nikl,N.Solovieva,A.Yoshikawa,YujiKagamitani,T.Fukuda 한양대학교 세라믹연구소 2003 Journal of Ceramic Processing Research Vol.4 No.3
Tb-doped Yb3Al5O12 and Y3Al5O12 single crystals were grown by the micropulling-down method in the form of rods of 2 mm diameter and a few cm in length. Emission spectra and decay times of Tb3+ luminescent centers were measured for Tb concentrations in a Y(Yb) sublattice of (1-70) %. A noticeable decrease of the emission intensity and decay time was obtained for Tb concentrations above 15% and 30% for Y3Al5O12 and Yb3Al5O12 hosts, respectively. Both effects are ascribed to the concentration quenching of Tb3+ luminescence due to energy migration over the Tb3+ subsystem and subsequent energy transfer to unspecified nonradiative traps. Energy migration process and structural aspects are discussed.
K. Tahara,Y. Fukuda,G. Wakabayashi,H. Ban,Y. Morimoto,M. Yoshioka,K. Kiyohara,Y. Koba,H. Iwamoto,Y. Uozumi,N. Matsufuji 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
We measured proton-production double differential cross sections (DDXs) by 290 MeV/u carbon beams on carbon, copper, lead targets at forward angles. The proton energies were measured with the spectrometer which consisted of GSO(Ce) crystals and plastic scintillators. The measured DDXs were compared with the calculated ones with PHITS code. The simulation results generally agreed with the measured ones. The measured results will be useful as the benchmark of existing simulation codes and for the future improvements.