1 tu darmstadt, germany — 2 osaka university, japan — 3 ithemba labs, south africa —

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

Neutrino Nucleosynthesis of Exotic, Odd-Odd Nuclei 138La and 180Ta

Peter von Neumann-Cosel Institut für Kernphysik, Technische Universität Darmstadt

S-DALINAC

TU DARMSTADT

Motivation

Neutrino nuclesynthesis of 138La and 180Ta

High resolution measurement of GT strength

Astrophysical implications

Outline

180Ta

138La

Exotic Nuclides

Nucleosynthesis of 138La

s-process r-process p-process

Production through Neutrino Processes

Neutral current reactions: 139La(,′n)138La 181Ta(,′n)180Ta

Charged current reactions: 138Ba(e,e)138La 180Hf(e,e)180Ta

Complete stellar evolution in massive stars with improved RPA calculations for -nucleus reactions

A. Heger et al., Phys. Lett. B 606 (2005) 258

138La: pure process production by cc reactions

Different Production Processes of 138La

180Ta: 50% process, 50% p process

Theoretical Prediction

Low neutrino energies small q L = 0 GT strength

RPA predicts main GT resonance well above neutron threshold Predictions for the low-lying strength are questionable

Experimental Requirements

(e,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

138La Spectrum

Target: 138BaCO4 embedded in polyvinylalcohol

RCNP

GT Strength Distribution in 138La

Cumulative Strength in 138La

B(GT–)exp 117% B(GT–)theo at 7.47 MeV

Cumulative Strength in 180Ta

B(GT–)exp 276% B(GT–)theo at 6.64 MeV

1

138La yield

Yields of 138La and 180Ta for a 15 M Star

solar

2

3

4

2

180Ta yield

solar

4

6

8

-process

ch. curr. 8 MeV

neut. curr.

ch. curr. 4 MeV

Branching ratio to 180Ta isomer about 35%

Conclusions

GT strength in 138La and 180Ta below particle threshold extracted

138La is essentially produced in the process

180Ta at least partially produced in the process

Full results: A. Byelikov et al., PRL 98, 082501 (2007)