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Author |
Fujita, Y. et al; Algora, A.; Estevez-Aguado, E; Molina, F; Rubio, B. |
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Title |
High-resolution study of Gamow-Teller excitations in the Ca-42(He-3,t)Sc-42 reaction and the observation of a “low-energy super-Gamow-Teller state” |
Type |
Journal Article |
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Year |
2015 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
91 |
Issue |
6 |
Pages |
064316 - 15pp |
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Abstract |
To study the Gamow-Teller (GT) transitions from the T-z = +1 nucleus Ca-42 to the T-z = 0 nucleus Sc-42, where T-z is the z component of isospin T, we performed a (p, n)-type (He-3, t) charge-exchange reaction at 140 MeV/nucleon and scattering angles around 0 degrees. With an energy resolution of 29 keV, states excited by GT transitions (GT states) could be studied accurately. The reduced GT transition strengths B(GT) were derived up to the excitation energy of 13 MeV, assuming the proportionality between the cross sections at 0 degrees and B(GT) values. The main part of the observed GT transition strength is concentrated in the lowest 0.611-MeV, J(pi) = 1(+) GT state. All the other states at higher energies are weakly excited. Shell-model calculations could reproduce the gross feature of the experimental B(GT) distribution, and random-phase-approximation calculations including an attractive isoscalar interaction showed that the 0.611-MeV state has a collective nature. It was found that this state has all of the properties of a “low-energy super-Gamow-Teller state.” It is expected that low-lying J(pi) = 1(+) GT states have T = 0 in the T-z = 0 nucleus Sc-42. However, T = 1 states are situated in a higher energy region. Assuming an isospin-analogous structure in A = 42 isobars, analogous T = 1, 1(+) states are also expected in Ca-42. Comparing the Ca-42(He-3, t)Sc-42 and Ca-42(p, p') spectra measured at 0 degrees, candidates for T = 1 GT states could be found in the 10-12-MeV region of Sc-42. They were all weakly excited. The mass dependence of the GT strength distributions in Sc isotopes is also discussed. |
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Address |
[Fujita, Y.; Fujita, H.; Adachi, T.; Susoy, G.; Hatanaka, K.; Hirota, K.; Ishikawa, D.; Matsubara, H.; Okamura, H.; Ong, H. J.; Suzuki, T.; Tamii, A.; Zenihiro, J.] Osaka Univ, Res Ctr Nucl Phys, Ibaraki, Osaka 5670047, Japan, Email: fujita@rcnp.osaka-u.ac.jp |
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Amer Physical Soc |
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English |
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ISSN |
0556-2813 |
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Conference |
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Notes |
WOS:000356928700001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2283 |
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Author |
Fujita, Y. et al; Algora, A.; Estevez-Aguado, E.; Molina, F.; Rubio, B. |
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Title |
High-resolution study of T-z =+2 ->+1 Gamow-Teller transitions in the Ca-44(3He,t)Sc-44 reaction |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
88 |
Issue |
1 |
Pages |
014308 - 18pp |
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Keywords |
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Abstract |
In order to study the Gamow-Teller (GT) transitions from the T-z = +2 nucleus Ca-44 to the T-z = +1 nucleus Sc-44, where T-z is the z component of isospin T, we performed the (p, n)-type (He-3, t) charge-exchange (CE) reaction at 140 MeV/nucleon and the scattering angles 0 degrees and 2.5 degrees. An energy resolution of 28 keV, that was realized by applying matching techniques to the magnetic spectrometer system, allowed the study of fragmented states. The GT transition strengths, B(GT), were derived up to the excitation energy (E-x) of 13.7 MeV assuming the proportionality between cross sections and B(GT) values. The total sum of B(GT) values in discrete states was 3.7, which was 31% of the sum-rule-limit value of 12. Shell model calculations using the GXPF1J interaction could reproduce the gross features of the experimental B(GT) distribution, but not the fragmentation of the strength. By introducing the concepts of isospin, properties of isospin analogous transitions and states were investigated. (i) Assuming isospin symmetry, the T-z = +2 -> +1 and T-z = -2 -> -1 mirror GT transitions should have the same properties, where the latter can be studied in the beta decay of Cr-44 to V-44. First, we confirmed that the beta-decay half-life T-1/2 of Cr-44 can be reproduced using the B(GT) distribution from the Ca-44(He-3, t) measurement. Then, the 0 degrees, (3He, t) spectrum was modified to deduce the “beta-decay spectrum” and it was compared with the delayed-proton spectrum from the Cr-44 beta decay. The two spectra were mostly in agreement for the GT excitations, but suppression of the proton decay was found for the T = 2 isobaric analog state (IAS). (ii) Starting from the T = 2 ground state of 44Ca, the (3He, t) can excite GT states (state populated by GT transitions) with T = 1, 2, and 3. On the other hand, the Ca-44(p, p') reaction can excite spin-M1 states (states populated by spin-M1 transitions) with T = 2 and 3 that are analogous to the T = 2 and 3 GT states, respectively. By comparing the spectra from these two reactions, a T value of 2 is suggested for several GT states in the E-x = 11.5-13.7 MeV region. (iii) It has been suggested that the T = 2, J(pi) = 0(+) double isobaric analog state (DIAS) at 9.338 MeV in the T-z = 0 nucleus Ti-44 forms an isospin-mixed doublet with a subsidiary 0(+) state at 9.298 MeV. Since no corresponding state was found in the T-z = +1 nucleus Sc-44, we suggest T = 0 for the subsidiary state. |
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Address |
[Fujita, Y.; Fujita, H.] Osaka Univ, Dept Phys, Toyonaka, Osaka 5600043, Japan, Email: fujita@rcnp.osaka-u.ac.jp |
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Amer Physical Soc |
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English |
Summary Language |
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ISSN |
0556-2813 |
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Conference |
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Notes |
WOS:000321839100001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1495 |
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Author |
Puppe, P.; Frekers, D.; Adachi, T.; Akimune, H.; Aoi, N.; Bilgier, B.; Ejiri, H.; Fujita, H.; Fujita, Y.; Fujiwara, M.; Ganioglu, E.; Harakeh, M.N.; Hatanaka, K.; Holl, M.; Kozer, H.C.; Lee, J.; Lennarz, A.; Matsubara, H.; Miki, K.; Orrigo, S.E.A.; Suzuki, T.; Tamii, A.; Thies, J.H. |
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Title |
High-resolution ((3)He,t) reaction on the double-beta decaying nucleus (136)Xe |
Type |
Journal Article |
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Year |
2011 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
84 |
Issue |
5 |
Pages |
051305 - 5pp |
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Keywords |
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Abstract |
A ((3)He, t) charge-exchange reaction experiment on the double-beta decaying nucleus (136)Xe has been performed at an incident energy of 420 MeV with the objective to measure the Gamow-Teller (GT) strength distribution in (136)Cs. The measurements have been carried out at the dispersion-matched WS beam line and the Grand Raiden spectrometer of the Research Center for Nuclear Physics in Osaka, where an energy resolution of 42 keV was achieved. A new gas cell with thin windows made of polyethylene naphthalate has been employed as a target. The extracted GT strength distribution is confronted with the rather long 2 nu beta beta decay half-life of (136)Xe. |
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[Puppe, P; Frekers, D; Holl, M; Lennarz, A; Thies, JH] Univ Munster, Inst Kernphys, D-48149 Munster, Germany |
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Publisher |
Amer Physical Soc |
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English |
Summary Language |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0556-2813 |
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Conference |
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Notes |
WOS:000297121900001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial |
810 |
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Author |
Fujita, Y.; Rubio, B.; Gelletly, W. |
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Title |
Spin-isospin excitations probed by strong, weak and electro-magnetic interactions |
Type |
Journal Article |
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Year |
2011 |
Publication |
Progress in Particle and Nuclear Physics |
Abbreviated Journal |
Prog. Part. Nucl. Phys. |
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Volume |
66 |
Issue |
3 |
Pages |
549-606 |
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Keywords |
Gamow-Teller transitions; beta decay; Charge-exchange reactions; Isospin symmetry; High resolution; Proton-rich nuclei |
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Abstract |
Gamow-Teller (GT) transitions are the most common weak interaction processes of spin-isospin (sigma tau) type in atomic nuclei. They are of interest not only in nuclear physics but also in astrophysics; they play an important role in supernovae explosions and nucleosynthesis. The direct study of weak decay processes, however, gives relatively limited information about GT transitions and the states excited via GT transitions (GT states); beta decay can only access states at excitation energies lower than the decay Q-value, and neutrino-induced reactions have very small cross-sections. However, one should note that beta decay has a direct access to the absolute GT transition strengths B(GT) from a study of half-lives, Q(beta)-values and branching ratios. They also provide information on GT transitions in nuclei far-from-stability. Studies of M1 gamma transitions provide similar information. In contrast, the complementary charge-exchange (CE) reactions, such as the (p, n) or ((3)He, t) reactions at intermediate beam energies and 0 degrees, can selectively excite GT states up to high excitation energies in the final nucleus. It has been found empirically that there is a close proportionality between the cross-sections at 0 degrees and the transition strengths B(GT) in these CE reactions. Therefore, CE reactions are useful tools to study the relative values of B(GT) strengths up to high excitation energies. In recent ((3)He, t) measurements, one order-of-magnitude improvement in the energy resolution has been achieved. This has made it possible to make one-to-one comparisons of GT transitions studied in CE reactions and beta decays. Thus GT strengths in ((3)He, t) reactions can be normalised by the beta-decay values. In addition, comparisons with closely related M1 transitions studied in gamma decay or electron inelastic scattering [(e, e')1, and furthermore with “spin” M I transitions that can be studied by proton inelastic scattering [(p, p')[ have now been made possible. In these comparisons, the isospin quantum number T and associated symmetry structure in the same mass A nuclei (isobars) play a key role. Isospin symmetry can extend our scope even to the structures of unstable nuclei that are far from reach at present unstable beam factories. |
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Address |
[Fujita, Y] Osaka Univ, Dept Phys, Osaka 5600043, Japan, Email: fujita@rcnp.osaka-u.ac.jp |
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Publisher |
Elsevier Science Bv |
Place of Publication |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0146-6410 |
ISBN |
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Conference |
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Notes |
WOS:000292473100003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
692 |
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