Isospin symmetry of Tz = ± 3/2 → ±1/2 Gamow-Teller transitions in A=41 nuclei

Y. Fujita, Y. Shimbara, T. Adachi, G. P.A. Berg, B. A. Brown, H. Fujita, K. Hatanaka, J. Kamiya, K. Nakanishi, Y. Sakemi, S. Sasaki, Y. Shimizu, Y. Tameshige, M. Uchida, T. Wakasa, M. Yosoi

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Abstract

Under the assumption that isospin I is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A. The strengths of Tz=+3/2→+1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A=41 isobar quartet are compared in detail. The Tz= +3/2+1/2 GT transitions from the Jπ=3/2+ ground state of 41K leading to excited Jπ = 1/2+, 3/2 +, and 5/2+ states in 41Ca were measured using the (3He,t) charge-exchange reaction. With a high energy resolution of 35 keV, many fragmented states were observed, and the GT strength distribution was determined up to 10 MeV excitation energy (Ex). The main part of the strength was concentrated in the Ex =4-6 MeV region. A shell-model calculation could reproduce the concentration, but not so well details of the strength distribution. The obtained distribution was further compared with two results of 41Ti βdecay studying the analogous Tz=-3/2→-1/2 GT strengths. They reported contradicting distributions. One-to-one correspondences of analogous transitions and analog states were assigned up to Ex=6 MeV in the comparison with one of these 41Ti β-decay results. Combining the spectroscopic information of the analog states in 41Ca and 41 Sc, the most probable Jπ values were deduced for each pair of analog states. It was found that 5/2+ states carry the main part of the observed GT strength, while much less GT strength was carried by 1/2+ and 3/2+ states. The gross features of the GT strength distributions for each J were similar for the isospin analogous Tz=±3/ 2→±1/2 transitions, but the details were somewhat different. From the difference of the distributions, isospin-asymmetry matrix elements of ≈8 keV were deduced. The Coulomb displacement energy, which is sensitive to the configuration of states, showed a sudden increase of about 50 keV at the excitation energy of 3.8 MeV. The strengths of several Ml transitions to the IAS in 41Ca were compared with the strengths of analogous GT transitions. It was found that ratios of the M1 and GT transition strengths were similar, suggesting that the contributions of the lτ term in M1 transitions are small.

Original languageEnglish
Pages (from-to)54311
Number of pages1
JournalPhysical Review C - Nuclear Physics
Volume70
Issue number5
DOIs
Publication statusPublished - Nov 2004

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics

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    Fujita, Y., Shimbara, Y., Adachi, T., Berg, G. P. A., Brown, B. A., Fujita, H., Hatanaka, K., Kamiya, J., Nakanishi, K., Sakemi, Y., Sasaki, S., Shimizu, Y., Tameshige, Y., Uchida, M., Wakasa, T., & Yosoi, M. (2004). Isospin symmetry of Tz = ± 3/2 → ±1/2 Gamow-Teller transitions in A=41 nuclei. Physical Review C - Nuclear Physics, 70(5), 54311. https://doi.org/10.1103/PhysRevC.70.054311