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1 TU Darmstadt, Germany — 2 Osaka University, Japan — 3 iThemba LABS, South Africa —

TU DARMSTADT. S-DALINAC. Neutrino Nucleosynthesis of Exotic, Odd-Odd Nuclei 138 La and 180 Ta. Peter von Neumann-Cosel Institut für Kernphysik, Technische Universität Darmstadt. A. Byelikov 1 , T. Adachi 2 , H. Fujita 3 , Y. Fujita 2 , A. Heger 4 , Y. Kalmykov 1 , K. Langanke 5 ,

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1 TU Darmstadt, Germany — 2 Osaka University, Japan — 3 iThemba LABS, South Africa —

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  1. TU DARMSTADT S-DALINAC Neutrino Nucleosynthesis of Exotic, Odd-Odd Nuclei 138La and 180Ta Peter von Neumann-Cosel Institut für Kernphysik, Technische Universität Darmstadt A. Byelikov1, T. Adachi2, H. Fujita3, Y. Fujita2, A. Heger4, Y. Kalmykov1, K. Langanke5, G. Martínez-Pinedo5, PvNC1, R. Neveling3, A. Richter1, A. Shevchenko1, Y. Shimbara2, F.D. Smit3, A. Tamii6, S.E. Woosley7 and M. Yosoi6 1TU Darmstadt, Germany — 2Osaka University, Japan — 3iThemba LABS, South Africa — 4LANL, USA, 5GSI Darmstadt, Germany — 6RCNP Osaka, Japan — 7UC Santa Cruz, USA

  2. Outline • Motivation • Neutrino nuclesynthesis of 138La and 180Ta • High resolution measurement of GT strength • Astrophysical implications

  3. Exotic Nuclides

  4. Nucleosynthesis of 138La s-process r-process p-process

  5. Production through Neutrino Processes • Neutral current reactions: 139La(n,n′n)138La • 181Ta(n,n′n)180Ta • Charged current reactions: 138Ba(ne,e-)138La • 180Hf(ne,e-)180Ta • Complete stellar evolution in massive stars with • improved RPA calculations for n-nucleus reactions A. Heger et al., Phys. Lett. B 606 (2005) 258

  6. Different Production Processes of 138La • 138La: pure n process production by cc reactions • 180Ta: 50% n process, 50% p process

  7. Theoretical Prediction • Low neutrino energies small q DL = 0 GT strength • RPA predicts main GT resonance well above neutron threshold • Predictions for the low-lying strength are questionable

  8. Experimental Requirements • (ne,e) Gamow-Teller strength (p,n) or (3He,t) • Gamow-Teller part narrow angle cut around 0° • Intermediate energies (100 – 400 MeV/u) • simple one-step reaction mechanism • spin – isospin response enhanced (3He,t) reaction at RCNP

  9. 138La Spectrum RCNP • Target: 138BaCO4 embedded in polyvinylalcohol

  10. GT Strength Distribution in 138La

  11. Cumulative Strength in 138La • B(GT–)exp» 117% B(GT–)theo at 7.47 MeV

  12. Cumulative Strength in 180Ta • B(GT–)exp» 276% B(GT–)theo at 6.64 MeV

  13. Yields of 138La and 180Ta for a 15 M Star 138La yield 180Ta yield g-process 4 8 neut. curr. ch. curr. 4 MeV 3 6 ch. curr. 8 MeV 2 4 solar 1 2 solar • Branching ratio to 180Ta isomer about 35%

  14. Conclusions • GT strength in 138La and 180Ta below • particle threshold extracted • 138La is essentially produced in the n process • 180Ta at least partially produced in the n process • Full results: • A. Byelikov et al., PRL 98, 082501 (2007)

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