In order to study the T-z = +1 -> 0 Gamow-Teller (GT) transitions in the mass A = 26 system, a charge-exchange reaction Mg-26(He-3,t)Al-26 was performed at an incident energy of 140 MeV/nucleon and scattering angle at and near 0 degrees, where T-z is the z component of isospin T defined by (N - Z)/2. In this (p, n)-type reaction, it is expected that GT states with T = 0, 1, and 2 are excited. An energy resolution of Delta E = 23 keV allowed us to study many discrete states. Most of the prominent states showed 0 degrees-peaked angular distributions, which suggested that they are the states excited by Delta L = 0 GT transitions. Candidates of GT states were studied up to an excitation energy E-x = 18.5 MeV. The reduced GT transition strengths, B(GT), were derived assuming the proportionality between cross sections and B(GT) values. Standard B(GT) values were obtained form the Si-26 beta decay, where the mirror symmetry of T-z = +/- 1 -> 0 GT transitions was assumed. The GT strength, as a whole, is divided in two energy regions: the region of up to 8.5 MeV and the higher-energy region of 8.5-12.8MeV, where the strength in the latter region distributed like a resonance. The obtained GT strength distribution is compared with the results of random phase approximation calculations. The T = 2 GT states are expected in the region E-x >= 13.5 MeV. By comparing with the results of (n, p)-type Mg-26(d, He-2)Na-26 and Mg-26(t, He-3)Na-26 reactions, the isospin symmetry of T = 2 GT states is discussed. Owing to the high-energy resolution, we could study the decay widths Gamma for the states in the E-x > 9 MeV region. The T = 2 state at 13.592 MeV is not noticeably wider than the experimental energy resolution. The narrow width of the state is explained in terms of isospin selection rules.

High-resolution study of T-z =+1 -> 0 Gamow-Teller transitions in the Mg-26(He-3,t)Al-26 reaction / K. Win, Y. Fujita, O. Yee Yee, H. Fujita, Y.F. Niu, T. Adachi, G.P.A. Berg, G. Colò, H. Dohmann, M. Dozono, D. Frekers, E.-. Grewe, K. Hatanaka, D. Ishikawa, R. Kehl, N.T. Khai, Y. Kalmykov, H. Matsubara, P. Von Neumann-Cosel, T. Niizeki, T. Ruhe, Y. Shimbara, K. Suda, A. Tamii, J. Thies, H.P. Yoshida. - In: PHYSICAL REVIEW C. - ISSN 2469-9985. - 96:6(2017 Dec 07). [10.1103/PhysRevC.96.064309]

High-resolution study of T-z =+1 -> 0 Gamow-Teller transitions in the Mg-26(He-3,t)Al-26 reaction

G. Colò;
2017

Abstract

In order to study the T-z = +1 -> 0 Gamow-Teller (GT) transitions in the mass A = 26 system, a charge-exchange reaction Mg-26(He-3,t)Al-26 was performed at an incident energy of 140 MeV/nucleon and scattering angle at and near 0 degrees, where T-z is the z component of isospin T defined by (N - Z)/2. In this (p, n)-type reaction, it is expected that GT states with T = 0, 1, and 2 are excited. An energy resolution of Delta E = 23 keV allowed us to study many discrete states. Most of the prominent states showed 0 degrees-peaked angular distributions, which suggested that they are the states excited by Delta L = 0 GT transitions. Candidates of GT states were studied up to an excitation energy E-x = 18.5 MeV. The reduced GT transition strengths, B(GT), were derived assuming the proportionality between cross sections and B(GT) values. Standard B(GT) values were obtained form the Si-26 beta decay, where the mirror symmetry of T-z = +/- 1 -> 0 GT transitions was assumed. The GT strength, as a whole, is divided in two energy regions: the region of up to 8.5 MeV and the higher-energy region of 8.5-12.8MeV, where the strength in the latter region distributed like a resonance. The obtained GT strength distribution is compared with the results of random phase approximation calculations. The T = 2 GT states are expected in the region E-x >= 13.5 MeV. By comparing with the results of (n, p)-type Mg-26(d, He-2)Na-26 and Mg-26(t, He-3)Na-26 reactions, the isospin symmetry of T = 2 GT states is discussed. Owing to the high-energy resolution, we could study the decay widths Gamma for the states in the E-x > 9 MeV region. The T = 2 state at 13.592 MeV is not noticeably wider than the experimental energy resolution. The narrow width of the state is explained in terms of isospin selection rules.
nuclear and high energy physics
Settore FIS/04 - Fisica Nucleare e Subnucleare
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/557121
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