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The astrophysical p-process

The astrophysical p-process. Zs. F ü l ö p ATOMKI Debrecen, Hungary. Open questions in physics. 1. What is dark matter? 2. What is dark energy? 4. Do neutrinos have mass? 5. Where do ultrahigh-energy particles come from?

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The astrophysical p-process

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  1. The astrophysical p-process Zs. Fülöp ATOMKI Debrecen, Hungary

  2. Open questions in physics 1. What is dark matter? 2. What is dark energy? 4. Do neutrinos have mass? 5. Where do ultrahigh-energy particles come from? 6. Is a new theory of light and matter needed to explain what happens at very high energies and temperatures? 7. Are there new states of matter at ultrahigh temperatures and densities? 8. Are protons unstable? 9. What is gravity? 10. Are there additional dimensions? 11. How did the Universe begin? 3. How were the heavy elements made? National Research Council Report (2003)

  3. A chance to answer

  4. Temperature -reaction rate • Nonexplosive scenario: • Low energy • Small cross sections • Extrapolation needed (S-factor) • → indirect methods + underground labs • Explosive scenario: • Higher energies • High cross sections • Exotic nuclei (low intensities) • → RIB Charged particle reaction cross sections are difficult to measure at astrophysical energies

  5. P-process: Gamow window reachable! • Low cross section → • High beam current • Energy range: 1-15 MeV/A • High efficiency detection • Background reduction • Enriched (and stable) target • In-beam and activation methods • No extrapolation is needed • Inclusive experiments Fülöp et al.: NPA758 (2005)

  6. P-NUCLEI • Heavy • Proton-rich • Even-even • Rare (0.1-1%) • Not accessible by r,s processes

  7. Overproduction Factors High abundance: 92Mo (14.8%), 94Mo (9.25%), 96Ru (5.5%), 98Ru (1.88%)

  8. Astrophysical p-process: an open issue • Site: SNII Supernova shock passing through O-Ne layers of progenitor star (T9=1-3) • Time scale: 1s • Gamma-induced reactions on s-process seed nuclei: (γ,n) reaction chain → proton rich region • Branching points: (γ,p) and/or (γ,α) • Alternative processes e.g. ν-reactions (Fröhlich: PRL 2007) • Alternative sites (Fujimoto:ApJ 2007)

  9. Reaction Network T1/2=108y Experimental charged particle rates are missing!

  10. Input Physics • Stellar models • Seed abundances • Nuclear reaction networks: • Hauser-Feshbach cross section calculations • Ingredients: ground state properties, level densities, optical potentials, γ-ray strength functions… ?? The reliability of the well-known and well tested HF calculations under p-process constraints

  11. 1992: a new collaboration with Bochum Aim: experimental verification of theoretical cross sections in the mass and energy range relevant to the astrophysical p-process using the low energy accelerators of ATOMKI Masterminds: C. Rolfs, E. Somorjai Postdoc: Zs. Fulop First result: 70Ge(α,γ)74Se European Workshop on Heavy Element Nucleosynthesis. Budapest, March 9-11,1994

  12. capture cross section measurements nuclear physics input: reaction rates, etc astrophysical input: seed abundances temperature time scale, etc. observed p-isotope abundances p-process model calculations p-process network calculations calculated p-isotope abundances

  13. masses, etc. level density optical model potential capture cross section measurements nuclear physics input: statistical model calculations astrophysical input: seed abundances temperature time scale, etc. observed p-isotope abundances Input parameters of the statistical models • Largenetworks • Lack /toomany of keyreactions • → Trend investigations • → Global studies p-process network calculations calculated p-isotope abundances

  14. Sensitivity studies • Reaction rate sensitivity • Branching point sensitivity • Statistical model sensitivity on input parameters (γ,p) (γ,n) (γ,α) W.Rapp et al.: ApJ 653 (2006) T.Rauscher: PRC 73 (2006)

  15. Stellar enhancement 148Gd(γ,α)144Sm 144Sm(α,γ)148Gd direct: Q>0 reverse: Q<0 > Mohr/Fülöp/Utsunomiya: EPJA 32 (2007) 357. G.G. Kiss et al: PRL 101 (2008) 191101.

  16. Experimental approaches A. Gamma induced studies(γ,n), (γ,p), (γ,α) • Brehmsstrahlungγ-source + activation (Darmstadt/Dresden) • Tagged γ-source + in-beam (Darmstadt) • Virtual γ→ Coulomb dissociation (GSI) B. Sub-Coulomb (p,γ), (p,n), (α,γ), (α,n), (α,p) + detailed balance • Activation (many labs incl. ATOMKI, Notre Dame, Karslruhe) • In-beam with 4π arrays: NaI (Bochum), HPGe (Köln), BaF2(Karlsruhe) • Storage ring: (p,γ) (ESR-GSI) • A + B complementary, bothneededforfullunderstanding • Study of differentchannelsleadingtoemergingfromthesamenucleus • Majority of publisheddata is byactivation

  17. In all cases applicable One target is enough Enriched targets Background problems Level scheme Angular distributions On-line γ-spectrometry Cons: Pros:

  18. 70Ge(α,γ)74Se: an example Fülöp et al: Z.Phys A 355 (1996) 203.

  19. Low background Natural target More reactions covered Limited applicability (abundance, branching, half-life, open channels) T1/2 dependent Many targets needed Beam monitoring Nleft to t1 t2 time Off-line γ-spectrometry Cons: Pros:

  20. 84,86,87Sr(p,γ)85,87,88Y: example Gy. Gyurky et al: PRC 64 (2001) 065803.

  21. Off-line spectrum

  22. Activation method: serious limitations • Poorly known nuclear parameters (branching, T1/2) • Ancillary experiments needed • Too long halflife • AMS: 142Nd(α,γ)146Sm (T1/2=108 y) @ANL • Inadequate branching ratios (no γ-transition) Characteristic X-ray detection might help

  23. Case study: 169Tm(α,γ/n)173/172Lu decay characteristics: G.G. Kiss et al: Phys. Lett. B 695 (2011) 419.

  24. 169Tm(α,γ)173Lu - 169Tm(α,n)172Lu LEPS detector

  25. X-ray detection: (α,γ) possibilities at heavy mass

  26. 144Sm(α,γ)148Gd: alpha detection Si-detector underground SSNTD Eα= 3.2 MeV Somorjai et al: A&A 333 (1998) 1112.

  27. Sensitivity for optical potentials Call for more reliable optical potentials 74Se(p,γ)75Br 144Sm(α,γ)148Gd ‘Experimental’ potential Somorjai et al.: A&A 333 (1998) 1112 Gyürky et al.: PRC 68 (2003) 055803

  28. (α,α) experiments at low energies Experimental constraints on the optical model parameters in the A>100 region • Precision scattering chamber • ~100% enriched targets • Experimental constraints on the optical model parameters in the A>100 region • Alternative: (n,α) studies Experimental cross section Theoretical cross section Experimental Optical potential (extrapolated)

  29. (α,α) Experiments at Low Energies

  30. (α,α) Experiments at Low Energies

  31. Impact on p-process network calculations (,n) (,n) 108Sn 110Sn 112Sn 114Sn (,n) (,) (,) (,) (,p) (,p) (,p) T = 2.0·109 K (,n) (,n) (,n) 106Cd 108Cd 110Cd old Main reaction flow based on the reaction rate new secondary branches Gyurky et al: PRC 74 (2006) 025805.

  32. Summary • p-process calculated abundances depend on HF calculations • Gamow window is reachable • In lack of bottleneck reaction hunt for global characteristics • Stay tuned for new astrophysical models!

  33. Outlook: the voice of NuPECC

  34. Supported by ERC, EUROCORES • ATOMKI group members: • C. Bordeanu (OTKA-fellow 2010-12) • J. Farkas (grad. student) • Zs. Fülöp • Gy. Gyürky (ERC-fellow) • Z. Halász (grad. student) • G.G. Kiss (postdoc) • E. Somorjai • T. Szücs (grad. student) • Z. Korkulu & A. Ornelas (ERASMUS students 2011) In collaboration with: T. Rauscher (statisticalmodel) I. Dillmann, R.Plag (KADoNIS) D. Galaviz/P. Mohr (elasticscattering)

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