Quenching of gamow-teller matrix elements and isovector magnetic moments in mirror nuclei

1969 ◽  
Vol 1 (16) ◽  
pp. 829-834 ◽  
Author(s):  
R. Leonardi ◽  
M. Rosa-Clot
2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Lotta Jokiniemi ◽  
Jouni Suhonen ◽  
Hiroyasu Ejiri

Neutrino-nuclear responses in the form of squares of nuclear matrix elements, NMEs, are crucial for studies of neutrino-induced processes in nuclei. In this work we investigate magnetic hexadecapole (M4) NMEs in medium-heavy nuclei. The experimentally derived NMEs,MEXP(M4), deduced from observed M4γtransition half-lives are compared with the single-quasiparticle (QP) NMEs,MQP(M4), and the microscopic quasiparticle-phonon model (MQPM) NMEsMMQPM(M4). The experimentally derived M4 NMEs are found to be reduced by a coefficientk≈0.29with respect toMQP(M4) and byk≈0.33with respect toMMQPM(M4). The M4 NMEs are reduced a little by the quasiparticle-phonon correlations of the MQPM wave functions but mainly by other nucleonic and nonnucleonic correlations which are not explicitly included in the MQPM. The found reduction rates are of the same order of magnitude as those for magnetic quadrupoleγtransitions and Gamow-Teller (GT) and spin-dipole (SD)βtransitions. The impacts of the found reduction coefficients on the magnitudes of the NMEs involved in astroneutrino interactions and neutrinoless double beta decays are discussed.


1996 ◽  
Vol 11 (14) ◽  
pp. 2419-2544 ◽  
Author(s):  
HERBERT WEIGEL

The description of baryons as soliton solutions of effective meson theories for three-flavor (up, down and strange) degrees of freedom is reviewed and the phenomenological implications are illuminated. In the collective approach the soliton configuration is equipped with baryon quantum numbers by canonical quantization of the coordinates describing the flavor orientation. The baryon spectrum resulting from exact diagonalization of the collective Hamiltonian is discussed. The prediction of static properties, such as the baryon magnetic moments and the Cabibbo matrix elements for semileptonic hyperon decays, are explored with regard to the influence of flavor symmetry breaking. In particular, the role of strange degrees of freedom in the nucleon is investigated for both the vector and axial vector current matrix elements. The latter are discussed extensively within the context of the proton spin puzzle. The influence of flavor symmetry breaking on the shape of the soliton is examined, and observed to cause significant deviations from flavor-covariant predictions on the baryon magnetic moments. Short range effects are incorporated by a chirally invariant inclusion of vector meson fields. These extensions are necessary for properly describing the singlet axial vector current and the neutron–proton mass difference. The effects of the vector meson excitations on baryon properties are also considered. The bound state description of hyperons and its generalization to baryons containing a heavy quark are illustrated. In the case of the Skyrme model a comparison is made between the collective quantization scheme and the bound state approach. Finally, the Nambu–Jona-Lasinio model is employed to demonstrate that hyperons can be described as solitons in a microscopic theory of the quark flavor dynamics. This is explained for both the collective and the bound state approaches to strangeness.


1984 ◽  
Vol 412 (3) ◽  
pp. 481-508 ◽  
Author(s):  
W. Bentz ◽  
A. Arima ◽  
H. Hyuga ◽  
K. Shimizu

1985 ◽  
Vol 31 (5) ◽  
pp. 1679-1690 ◽  
Author(s):  
S. M. Grimes ◽  
J. D. Anderson ◽  
J. C. Davis ◽  
R. H. Howell ◽  
C. Wong ◽  
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1987 ◽  
Vol 65 (6) ◽  
pp. 609-613 ◽  
Author(s):  
Sam M. Austin ◽  
N. Anantaraman ◽  
J. S. Winfield

Heavy-ion reactions can be powerful probes for spin-transfer strength in nuclei, provided their reaction mechanism is simple so that a correlation can be established between cross sections and the relevant matrix elements. We discuss the desirable features of heavy-ion reactions in general and a series of tests of reaction mechanisms that have been carried out for two of the most favorable reactions; (6Li, 6He) and (12C, 12N). We establish that the (6Li, 6He) reaction is one-step in nature above 25 MeV∙nucleon−1 and establish a calibration function relating cross sections and Gamow–Teller matrix elements. We also find that the (12C, 12N) reaction is likely to be dominated by the one-step process above about 50 MeV∙nucleon−1.


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