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Nuclear astrophysics data needs for charged-particle reactions C. Iliadis

Nuclear astrophysics data needs for charged-particle reactions C. Iliadis (University of North Carolina). In which sites are charged-particle reactions important? For any object in the Universe that produces nuclear energy For which processes would we like to know the reaction rates?

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Nuclear astrophysics data needs for charged-particle reactions C. Iliadis

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  1. Nuclear astrophysics data needs for charged-particle reactions C. Iliadis (University of North Carolina)

  2. In which sites are charged-particle reactions important? For any object in the Universe that produces nuclear energy For which processes would we like to know the reaction rates? Big bang Hydrogen burning Helium burning Advanced burning (carbon/neon/oxygen/silicon) s-process (neutron sources) p-process . . .

  3. A list of “experimental” charged-particle reaction rate compilations: Brussels (Angulo, Descouvemont) *Chapel Hill (Iliadis) Karlsruhe (KADoNIS) Livermore (Hoffman, Rauscher, Heger, Woosley) Los Alamos (Hale, Page) *MSU (Schatz) NACRE (Angulo et al.) NETGEN (Arnould, Goriely, Jorissen) *Notre Dame (Wiescher) *Oak Ridge (Smith, Hix, Bardayan et al.) . . . *: REACLIB format

  4. Published “experimental” charged particle reaction rate evaluations: Reference: # of reactions: Mass range: • CONCLUSION: • About 66 reactions from CF88 have not been evaluated since! • Many of these are still used in our rate libraries (e.g., REACLIB)

  5. How an incorrect reaction rate was derived from “correct” input information:

  6. 3 Nonresonant s (R-matrix) 4 Insufficient resonance information 2 Unobserved resonances 1 Measured Er and wg S-factor Energy What is needed in terms of experimental input information? Reaction rate:

  7. 3 Nonresonant s (R-matrix) 4 Insufficient resonance information 2 Unobserved resonances 1 Measured Er and wg S-factor Energy

  8. Region 1: Absolute resonance strengths and cross sections Paine et al., PR C17, 1550 (1978)

  9. Recommended absolute resonance strengths as a backbone for reaction rate evaluations: Iliadis et al., A=20-40 evaluation These recommended wg values are independent of target or beam properties!

  10. 3 Nonresonant s (R-matrix) 4 Insufficient resonance information 2 Unobserved resonances 1 Measured Er and wg S-factor Energy

  11. Er A+a X+x C Region 2: “Indirect” experimental information is crucial for low-energy resonances y a C2S large Intensity of y Ey C2S small

  12. Reliability of indirect measurements: • (see also talks tomorrow by Rauscher/Descouvemont) • Orsay/spectroscopic factors (Vernotte et al.) • Texas A&M/ANC’s (Tribble, Mukhamedzhanov et al.) • . • . • .

  13. 3 Nonresonant s (R-matrix) 4 Insufficient resonance information 2 Unobserved resonances 1 Measured Er and wg S-factor Energy

  14. Region 3: Extrapolation of nonresonant cross sections R-matrix model Examples: 7Be(p,g)8B 12C(a,g)16O 14N(p,g)15O . . . S-factor Gamow peak Energy (see talk tomorrow by Descouvemont)

  15. 3 Nonresonant s (R-matrix) 4 Insufficient resonance information 2 Unobserved resonances 1 Measured Er and wg S-factor Energy

  16. Region 4: Matching of experimental and Hauser-Feshbach rates In recent evaluations (Angulo 1999, Iliadis 2001), experimental and theoretical rates are matched at Tmax which is found from the condition: E0(Tmax)+nD(Tmax)=Emax Experimental cutoff at high energy Emax E0 D Gamow peak D S-factor Energy Fowler & Hoyle, ApJS 9, 201 (1964)

  17. Blue: Gamow peak Red: effective window

  18. Reaction rate errors: NACRE as a milestone Iliadis et al., ApJS 134, 151 (2001) See also: Thompson and Iliadis, NPA 647, 259 (1999) [Error analysis for resonant thermonuclear Reaction rates] Mathematical model for error analysis if values and uncertainties for Er, wg and C2S are know Download from: www.tunl.duke.edu/~astro/Software/Software.html

  19. A new reaction rate evaluation effort: Charged-particle rates in the A=40-60 region Parpottas (U. of Cyprus) Iliadis (UNC)

  20. The future: • Use recommended standard resonance strengths and cross sections • Refine indirect methods (C2S, ANC’s) • Apply a sound mathematical model to derive rate errors • Use primary data to calculate reaction rates • A unified reaction rate evaluation effort would be important for our field • A modular reaction rate library generator like NETGEN is useful

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