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Title: Gamow-Teller Strength in the Exotic Odd-Odd Nuclei {sup 138}La and {sup 180}Ta and Its Relevance for Neutrino Nucleosynthesis

Abstract

The Gamow-Teller strength distributions below the particle threshold in {sup 138}La and {sup 180}Ta, deduced from high-resolution measurements of the ({sup 3}He,t) reaction at 0 deg., allow us to evaluate the role of charged-current reactions for the production of these extremely rare nuclides in neutrino-nucleosynthesis models. The analysis suggests that essentially all {sup 138}La in the Universe can be made that way. Neutrino nucleosynthesis also contributes significantly to the abundance of {sup 180}Ta but the magnitude depends on the unknown branching ratio for population of the long-lived isomer.

Authors:
; ; ; ;  [1]; ; ;  [2];  [3];  [4]; ; ; ; ; ; ; ; ; ;  [5] more »;  [6];  [7] « less
  1. Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany)
  2. Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan)
  3. School of Physics, University of the Witwatersrand, PO Wits, Johannesburg 2050 (South Africa)
  4. (South Africa)
  5. Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047 (Japan)
  6. Theoretical Astrophysics Group, MS B227, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  7. (United States) (and others)
Publication Date:
OSTI Identifier:
20960140
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevLett.98.082501; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ABUNDANCE; BRANCHING RATIO; GAMOW-TELLER RULES; HELIUM 3 BEAMS; HELIUM 3 REACTIONS; ISOMERS; LANTHANUM 138; NEUTRINOS; NUCLEOSYNTHESIS; TANTALUM 180

Citation Formats

Byelikov, A., Kalmykov, Y., Neumann-Cosel, P. von, Richter, A., Shevchenko, A., Adachi, T., Fujita, Y., Shimbara, Y., Fujita, H., iThemba LABS, PO Box 722, Somerset West 7129, Fujita, K., Hatanaka, K., Kawase, K., Nakanishi, K., Sakamoto, N., Sakemi, Y., Shimizu, Y., Tameshige, Y., Tamii, A., Yosoi, M., Heger, A., and Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064. Gamow-Teller Strength in the Exotic Odd-Odd Nuclei {sup 138}La and {sup 180}Ta and Its Relevance for Neutrino Nucleosynthesis. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.082501.
Byelikov, A., Kalmykov, Y., Neumann-Cosel, P. von, Richter, A., Shevchenko, A., Adachi, T., Fujita, Y., Shimbara, Y., Fujita, H., iThemba LABS, PO Box 722, Somerset West 7129, Fujita, K., Hatanaka, K., Kawase, K., Nakanishi, K., Sakamoto, N., Sakemi, Y., Shimizu, Y., Tameshige, Y., Tamii, A., Yosoi, M., Heger, A., & Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064. Gamow-Teller Strength in the Exotic Odd-Odd Nuclei {sup 138}La and {sup 180}Ta and Its Relevance for Neutrino Nucleosynthesis. United States. doi:10.1103/PHYSREVLETT.98.082501.
Byelikov, A., Kalmykov, Y., Neumann-Cosel, P. von, Richter, A., Shevchenko, A., Adachi, T., Fujita, Y., Shimbara, Y., Fujita, H., iThemba LABS, PO Box 722, Somerset West 7129, Fujita, K., Hatanaka, K., Kawase, K., Nakanishi, K., Sakamoto, N., Sakemi, Y., Shimizu, Y., Tameshige, Y., Tamii, A., Yosoi, M., Heger, A., and Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064. Fri . "Gamow-Teller Strength in the Exotic Odd-Odd Nuclei {sup 138}La and {sup 180}Ta and Its Relevance for Neutrino Nucleosynthesis". United States. doi:10.1103/PHYSREVLETT.98.082501.
@article{osti_20960140,
title = {Gamow-Teller Strength in the Exotic Odd-Odd Nuclei {sup 138}La and {sup 180}Ta and Its Relevance for Neutrino Nucleosynthesis},
author = {Byelikov, A. and Kalmykov, Y. and Neumann-Cosel, P. von and Richter, A. and Shevchenko, A. and Adachi, T. and Fujita, Y. and Shimbara, Y. and Fujita, H. and iThemba LABS, PO Box 722, Somerset West 7129 and Fujita, K. and Hatanaka, K. and Kawase, K. and Nakanishi, K. and Sakamoto, N. and Sakemi, Y. and Shimizu, Y. and Tameshige, Y. and Tamii, A. and Yosoi, M. and Heger, A. and Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064},
abstractNote = {The Gamow-Teller strength distributions below the particle threshold in {sup 138}La and {sup 180}Ta, deduced from high-resolution measurements of the ({sup 3}He,t) reaction at 0 deg., allow us to evaluate the role of charged-current reactions for the production of these extremely rare nuclides in neutrino-nucleosynthesis models. The analysis suggests that essentially all {sup 138}La in the Universe can be made that way. Neutrino nucleosynthesis also contributes significantly to the abundance of {sup 180}Ta but the magnitude depends on the unknown branching ratio for population of the long-lived isomer.},
doi = {10.1103/PHYSREVLETT.98.082501},
journal = {Physical Review Letters},
number = 8,
volume = 98,
place = {United States},
year = {Fri Feb 23 00:00:00 EST 2007},
month = {Fri Feb 23 00:00:00 EST 2007}
}
  • Gamow-Teller (GT) strength transitions are an ideal probe for testing nuclear structure models. In addition to nuclear structure, GT transitions in nuclei directly affect the early phases of Type Ia and Type-II supernovae core collapse since the electron capture rates are partly determined by these GT transitions. In astrophysics, GT transitions provide an important input for model calculations and element formation during the explosive phase of a massive star at the end of its life-time. Recent nucleosynthesis calculations show that odd-odd and odd-A nuclei cause the largest contribution in the rate of change of lepton-to-baryon ratio. In the present manuscript,more » we have calculated the GT strength distributions and electron capture rates for odd-odd nucleus {sup 50}V by using the pn-QRPA theory. At present {sup 50}V is the first experimentally available odd-odd nucleus in fp-shell nuclei. We also compare our GT strength distribution with the recently measured results of a {sup 50}V(d, {sup 2}He){sup 50}Ti experiment, with the earlier work of Fuller, Fowler, and Newman (referred to as FFN) and subsequently with the large-scale shell model calculations. One curious finding of the paper is that the Brink's hypothesis, usually employed in large-scale shell model calculations, is not a good approximation to use at least in the case of {sup 50}V. SNe Ia model calculations performed using FFN rates result in overproduction of {sup 50}Ti, and were brought to a much acceptable value by employing shell model results. It might be interesting to study how the composition of the ejecta using presently reported QRPA rates compare with the observed abundances.« less
  • The cosmological origins of the two heaviest odd-odd nuclei {sup 138}La and {sup 180}Ta are believed to be closely related to the neutrino process. We investigate in detail neutrino-induced reactions on the nuclei. Charged current (CC) reactions {sup 138}Ba({nu}{sub e},e{sup -}){sup 138}La and {sup 180}Hf({nu}{sub e},e{sup -}){sup 180}Ta are calculated using the standard quasi-particle random phase approximation (QRPA) with neutron-proton pairing as well as neutron-neutron and proton-proton pairing correlations. For the neutral current (NC) reactions {sup 139}La({nu},{nu}{sup '}){sup 139}La{sup *} and {sup 181}Ta({nu},{nu}{sup '}){sup 181}Ta{sup *}, we generate ground and excited states of the odd-even target nuclei {sup 139}La andmore » {sup 181}Ta by operating one quasiparticle to even-even nuclei {sup 138}Ba and {sup 180}Hf, which are assumed as the BCS ground state. Numerical results for CC reactions are shown to be consistent with recent semiempirical data deduced from the Gamow-Teller strength distributions measured in the ({sup 3}He,t) reaction. Results for NC reactions are estimated to be about 4 to 5 times smaller than the results for CC reactions. Finally, cross sections weighted by the incident neutrino flux in the core-collapse supernova are presented for further applications to the network calculations for relevant nuclear abundances.« less
  • Cross sections for the charge-exchange reaction (d,{sup 2}He) on {sup 50}V, the only odd-odd stable nucleus in the pf shell, have been measured at an incident energy of 171 MeV. The two correlated protons of the unbound {sup 2}He system were both momentum analyzed and detected by the same spectrometer and detector. Measurements have been carried out at forward center-of-mass angles up to 6 deg. The GT{sup +} strength distribution has been extracted up to about 12 MeV of excitation energy. Because charge-exchange reactions from {sup 50}V provide a unique opportunity to probe Gamow-Teller response from an odd-odd nucleus ofmore » the pf shell, the present study serves as important test case for model calculations and astrophysical processes that proceed through GT-type transitions. Consequently, the experimental result is compared with a large-scale shell-model calculation, and the implications for electron-capture processes in presupernova environments are discussed.« less
  • We analyze the production and freeze-out of the isomer {sup 180}Ta{sup m} in the {nu}-process. We consider the influence of a possible low-lying intermediate (J=5) state at 592 keV using a transition width estimated from the measured half-life. This more realistic width is much smaller than the previous estimate. We find that the 592-keV state leads only to a small reduction of the residual isomer population ratio from the previous result; that is, considering this better estimate for the transition width, the isomer population ratio changes from R=0.39 to R=0.38, whereas previously it was estimated that this transition could reducemore » the ratio to R=0.18. This finding strengthens the evidence that {sup 138}La and {sup 180}Ta are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of kT{approx_equal}4 MeV.« less
  • We compare the Gamow-Teller strength distributions for the [ital A]=37 system as measured by the [sup 37]Ca [beta][sup +] decay experiment with [sup 37]Cl ([ital p],[ital n]) experiments, considering the effect of suppression of [beta]-delayed protons from the 3.239-MeV state in [sup 37]K. We determine a range of values for the suppression of proton emission from this state for which the two measurements of strength are consistent. Recent studies of this state support this suppression and the amount of suppression is within our allowed range. Using the experimentally determined value for the suppression we are able to determine neutrino crossmore » sections on [sup 37]Cl from [sup 8]B solar neutrinos, supernova neutrinos, and [mu][sup +] decay neutrinos. Our cross section for [mu][sup +] decay neutrinos is found to be 20% larger than the estimates of Bahcall, because of high-lying strength only recently confirmed by the [sup 37]Ca [beta][sup +] decay experiment.« less