Shell model applications in nuclear astrophysics

1. Shell model applications in nuclear astrophysics Karlheinz Langanke GSI Helmholtzzentrum Darmstadt Technische Universität Darmstadt Shell model and nuclear structure – Ischia, May 14, 2014 In honor of Aldo Covello

2. Closer look on • electroncapture in presupernovaphase (nuclearcomposition A ~ 60) - electroncaptureduringcollapse (nuclearcomposition A > 65) - r-process in neutronstarmergers

3. Supernova: schematic view courtesy: R. Diehl

4. Electron capture: Lab vs Stars Capture is dominated by Gamow-Teller transitions During collapse, electrons are described by Fermi-Dirac distribution with chemical potentials of order a few MeV Parent nuclei are described by thermal ensemble

5. Calculating stellar capture rates data KVI Groningen Capture on nuclei in mass range A~45-65 calculated by large-scale shell model Capture rates are noticeably smaller than assumed before!

6. Consequences of capture rates Heger Woosley Martinez Pinedo important changes in collapse trajectory shell model rates for Fe-Ni nuclei slower by order of magnitude

7. Experiment vs shell model Cole, Zegers et al., PRC 86 (2012) 015809 Iron-nickel mass range under control With increasing density, less sensitivity to details of GT distribution -> models less sophisticated than shell model suffice, e.g. QRPA

8. Abundances in Type Ia‘s Type Ia‘s have produced about half of the abundance of nickel-iron range nuclei in the Universe Modern electron capture rates solve inconstency problem in Type Ia supernova abundance production Martinez-Pinedo, Thielemann

9. Abundance distribution during collapse Electron captures drive nuclear composition towards neutron-rich unstable nuclei

10. Unblocking GT for nuclei with neutron numbers N>40 In Independent Particle Model, GT are Pauli-blocked for N>40 In reality, blocking does not occur due to correlations and finite T. Calculations of rates by SMMC/RPA model.

11. Experimental GT distributions courtesy Dieter Frekers

12. Neutron occupancies Data from transfer reactions: J.P Schiffer and collaborators

13. Convergence with truncation level Cross-shell correlations converge slowly. Hence, models like thermofield dynamics model or finite temperature QRPA, which consider only 2p-2h correlations, do not suffice. (Zhi et al.)

14. Consequences of shell model rates Janka, Rampp, Martinez-Pinedo

15. Making Gold! Nature vs Humans Old stars in galactic halo have the same r-process abundances as the solar system for A>130, but not below. two distinct r-process sites? Johann Friedrich Böttger, Alchemist Inventor of European White China In Meissen, Germany

16. The R-Process • Masses • Half lives • Neutron capture rates • Fission • Neutrino reactions Courtesy: K.-L. Kratz

17. Potential r-process sites Neutrino-driven wind from a nascent neutron star in a supernova explosion (Woosley et al.) simulations show that conditions allow only for production upto second r-process peak Neutron star mergers Freiburghaus et al.

18. Trajectories and reheating After initial adiabatic expansion and cooling, the nuclear reactions (mainly beta decays) lead to a reheating of the ejected matter. The temperatures are high enough to establish an (n,gamma)<>(gamma,n) equilibrium. Due to the extreme neutron densities, the r-process path runs through nuclei not far from the neutron dripline. A. Bauswein, H.-Th. Janka

19. Abundance evolution in ns merger third peak produced like in classical r-process (neutron captures, beta decays) second peak produced by fission yields neutron captures after freeze-out lead peak produced by late alpha decays Mendoza, Martinez-Pinedo...

20. Dependence of half lives Eichler, Thielemann et al. faster half lives shift the peak back in mass number due to faster consumption of neutrons

21. Half lives around N=126 shell model: forbidden transitions important (Suzuki et al. Zhi et al.) data in neighborhood of N=126 show that half-lives are faster than believed (T. Nieto, KH. Schmidt et al.) faster matter flow through N=126 waiting points, faster consumption of neutrons faster fission cycling

22. abundances and mass models Mendoza, Martinez-Pinedo et al. quite unsensitive to mass models, fission cycling dominates ns merger -> robust abundance pattern, like in old stars?

23. Next-Generation Isotope Facilities GSI/FAIR TRIUMF/ ARIEL MSU/FRIB SPIRAL2 Isolde RIKEN/ RIBF

24. Google Earth: FAIR in 2020 in 2020 Austria China Finnland France Germany Greece India Italy Poland Romania Russia Slovakia Slovenia Spain Sweden Great Britain

25. Rare-Isotope Production Target Antiproton Production Target Observers CN DE ES FI FR GB GR IN IT PL RO RU SE SIS 100/300 GSI today Future facility SIS 18 UNILAC CBM ESR Super FRS HESR PP / AP FLAIR RESR CR NESR 100 m

26. RIBF contribution: masses FAIR

27. Impact of nuclear half-lives Impact of nuclear half-liveson r-process abundances Knowing the half-lives we will constrain the dynamics of the supernova explosion

28. The RIB Chance: New Horizons