Energy systematics of the giant gamow-teller resonance and a charge-exchange dipole spin-flip resonance

Hören, D.J.; Goodman, C.D.; Bainum, D.E.; Foster, C.C.; Gaarde, C.; Goulding, C.A.; Greenfield, M. B.; Rapaport, J.; Taddeucci, T. N.; Sugarbaker, E.; Masterson, T.; Austin, Sam M.; Galonsky, A.; Sterrenburg, W.A.

doi:10.1016/0370-2693(81)90553-0

Cited by 140 publications

(16 citation statements)

References 12 publications

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“…These experiments demonstrated the existence of very collective spin-isospin modes in nuclei (Moake et aL, 1979;Anderson et aL, 1980;Bainum et aL, 1980;Goodman et aL, 1980;Horen et aL, , 1981Gaarde et aL, 1981). Figure 1 shows measured zero-degree (p,n) spectra of various targets at an incident energy of E p = 200 MeV (from Gaarde et aL, 1981).…”

Section: A the Gamow-teller (Gt) Resonancementioning

confidence: 89%

Nuclear spin and isospin excitations

1992

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A review is given of our present knowledge of collective spin-isospin excitations in nuclei. Most of this knowledge comes from intermediate-energy charge-exchange reactions and from inelastic electron-and proton-scattering experiments. The nuclear-spin dynamics is governed by the spin-isospin-dependent two-nucleon interaction in the medium. This interaction gives rise to collective spin modes such as the giant Gamow-Teller resonances. An interesting phenomenon is that the measured total Gamow-Teller transition strength in the resonance region is much less than a model-independent sum rule predicts. Two physically different mechanisms have been discussed to explain this so-called quenching of the total Gamow-Teller strength: coupling to subnuclear degrees of freedom in the form of A-isobar excitation and ordinary nuclear configuration mixing. Both detailed nuclear structure calculations and extensive analyses of the scattering data suggest that the nuclear configuration mixing effect is the more important quenching mechanism, although subnuclear degrees of freedom cannot be ruled out. The quenching phenomenon occurs for nuclear-spin excitations at low excitation energies {co~ 10-20 MeV) and smallmomentum transfers {q < 0.5 fm~ *). A completely opposite effect is anticipated in the high (&>,#)-transfer region (0 < (o < 500 MeV, 0.5 < q < 3 fm~1). The nuclear spin-isospin response might be enhanced due to the attractive pion field inside the nucleus. Charge-exchange reactions at GeV incident energies have been used to study the quasifree peak region and the A-resonance region. An interesting result of these experiments is that the A excitation in the nucleus is shifted downwards in energy relative to the A excitation of the free proton. The physical origin of this shift is discussed, and it is shown that it may be related to the energy-dependent, attractive one-pion exchange interaction in the medium.

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Section: A the Gamow-teller (Gt) Resonancementioning

confidence: 89%

Nuclear spin and isospin excitations

1992

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“…The isovector dipole constants obtained from the calculation of the giant E1 resonance position are taken from [20]. The isovector constants for the GT and spin-dipole forces are obtained from the comparison of our calculations with the experimental data on 169Tm and of the empirical curve of the GT and spin-dipole resonances presented in [2]. In our calculations ~c[ =~ = 17/A MeV, which is 1.4 times as small as that in [3] due to the inclusion of a large number of singleparticle states.…”

Section: T(-)i 2 # I)l 2 -~ I(ir a Yxu T(+~l 2 # I)l Z }mentioning

confidence: 99%

“…The charge-exchange resonances are detected on the deformed 169Tm nucleus (see Refs. [2,3]). Theoretically, the chargeexchange resonances have been studied in many papers [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 96%

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Description of charge-exchange resonances in deformed nuclei

1984

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“…Charge exchange reactions [36,37,38] have revealed, still, that the spin-isospin residual forces can to some extent overcome this SU(4) symmetry breaking by transferring a substantial amount of the non-spin flip strength to higher energies (and build up in this way the GT resonance). 2 We may point out that it is not possible to obtain similar results in the Tamm-Dancoff approximation (TDA) where the GSC are neglected.…”

Section: Introductionmentioning

confidence: 99%

Double-beta decay in pn-QRPA model with isospin and SU(4) symmetry constraints

Krmpotić

Sharma

1994

Nuclear Physics A

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The transition matrix elements for the 0 + → 0 + double beta decays are calculated for 48 Ca, 76 Ge, 82 Se, 100 Mo, 128 T e and 130 T e nuclei, using a δ-interaction. As a guide, to fix the particle-particle interaction strengths, we exploit the fact that the missing symmetries of the mean field approximation are restored in the random phase approximation by the residual interaction. Thus, the T = 1, S = 0 and T = 0, S = 1 coupling strengths have been estimated by invoking the partial restoration of the isospin and Wigner SU (4) symmetries, respectively. When this recipe is strictly applied, the calculation is consistent with the experimental limit for the 2ν lifetime of 48 Ca and it also correctly reproduces the 2ν lifetime of 82 Se. In this way, however, the two-neutrino matrix elements for the remaining nuclei are either underestimated (for 76 Ge and 100 Mo) or overestimated (for 128 T e and 130 T e) approximately by a factor of 3. With a comparatively small variation (< 10%) of the spin-triplet parameter, near the value suggested by the SU(4) symmetry, it is possible to reproduce the measured T 2ν 1/2 in all the cases. The upper limit for the effective neutrino mass, as obtained from the theoretical estimates of 0ν matrix elements, is < m ν > ∼ = 1 eV. The dependence of the nuclear matrix elements on the size of the configuration space has been also analyzed. † Fellow of the CONICET from Argentina * Financial support from CNPq, Brazil is acknowledged

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Energy systematics of the giant gamow-teller resonance and a charge-exchange dipole spin-flip resonance

Abstract: In a series of papers1-5) in the early 1960ts, factor of two with increasing proton energy between We have used the beam-swinger f acility13) at IUCF, protons with incident energies of 120, 160, and 200MeV, and neutron flight paths of 60-70m to study the

Cited by 140 publications

References 12 publications

Nuclear spin and isospin excitations

Nuclear spin and isospin excitations

Description of charge-exchange resonances in deformed nuclei

Double-beta decay in pn-QRPA model with isospin and SU(4) symmetry constraints

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