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? Big bang Hydrogen burning Helium burning Advanced burning (carbon/neon/oxygen/silicon) s-process (neutron sources) p-process.

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

Published “experimental” charged particle reaction rate evaluations: CONCLUSION: About 66 reactions from CF88 have not been evaluated since! Many of these are still used in our rate libraries (e.g., REACLIB) Caughlan and Fowler, ADNDT 40, 283 (1988)159A=1-30 Angulo et al., NP A656, 3 (1999)86A=1-28 Iliadis et al., ApJS 134, 151 (2001)55A=20-40 Descouvemont et al., ADNDT 88, 203 (2004)10A=1-7 Reference: # of reactions: Mass range:

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

What is needed in terms of experimental input information? Reaction rate: Measured E r and  Unobserved resonances Nonresonant  (R-matrix) Insufficient resonance information Energy S-factor

Measured E r and  Unobserved resonances Nonresonant  (R-matrix) Insufficient resonance information Energy S-factor

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

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

Measured E r and  Unobserved resonances Nonresonant  (R-matrix) Insufficient resonance information Energy S-factor

Region 2: “Indirect” experimental information is crucial for low-energy resonances ErEr C A+a X+x a y EyEy Intensity of y C 2 S large C 2 S small

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.).

Measured E r and  Unobserved resonances Nonresonant  (R-matrix) Insufficient resonance information Energy S-factor

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

Measured E r and  Unobserved resonances Nonresonant  (R-matrix) Insufficient resonance information Energy S-factor

Region 4: Matching of experimental and Hauser-Feshbach rates In recent evaluations (Angulo 1999, Iliadis 2001), experimental and theoretical rates are matched at T max which is found from the condition: E 0 (T max )+n  (T max ) =E max Energy S-factor Experimental cutoff at high energy E max E0E0  Gamow peak  Fowler & Hoyle, ApJS 9, 201 (1964)

Blue: Gamow peak Red: effective window

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] Download from: Mathematical model for error analysis if values and uncertainties for E r,  and C 2 S are know

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

The future: Use recommended standard resonance strengths and cross sections Refine indirect methods (C 2 S, 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