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Continuum shell model calculations for nucleon capture at astrophysical energies

Continuum shell model calculations for nucleon capture at astrophysical energies. Janina Grinevi ciute Western Michigan University. H burning pp chain. 7 Be(p,  ) 8 B. Production rate of 8 Be solar neutrinos: accuracy of stellar models neutrino mixing and nature of weak interaction

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Continuum shell model calculations for nucleon capture at astrophysical energies

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  1. Continuum shell model calculations for nucleon capture at astrophysical energies Janina Grineviciute Western Michigan University

  2. H burning pp chain

  3. 7Be(p,)8B Production rate of 8Be solar neutrinos: • accuracy of stellar models • neutrino mixing and nature of weak interaction desired reaction rate uncertainty less than 5%

  4. Dependance on temperature of energy production rates

  5. CNO cycle figure taken from H. Schatz (2004)

  6. 4 CNO cycles figure taken from H. Schatz (2004)

  7. 14N(p,)15O Slowest reaction in CNO cycle • controls duration of hydrogen burning • determines main sequence turnoff – globular cluster ages • determines CNO neutrino flux in the Sun Initial abundance of C, N,O is mostly converted into 14N

  8. Turn off luminosity – age of globular clusters CNO cycle pp chain

  9. Proton capture reactions Crossections are extremely low  measure as low in energy as possible, then extrapolate to Gamow window

  10. 12 c(p,g) Cross section, barns 12C(p,g)13N

  11. 12C(p,g) S-factor

  12. RCCSM advantages R.J.Phillpott • Provides coupled-channels solutions for bound and unbound wave functions • Wave functions antisymmetric and contain no spurious components • Bound states and continuum states are orthogonal

  13. RCCSM coordinates

  14. RCCSM input • Oscillator size parameter n0=mw/ • Desired states of the A-1 core nuclei • Realistic translationally invariant interaction

  15. Interaction • A fit to Cohen-Kurath interaction and Reid soft core g-matrix elements • Spin orbit force • Tensor force • Skyrme interaction

  16. Channel wave functions within channel radius ac

  17. Calculations • Oscillator size parameter, interaction • R matrix radii • Calculate matrix elements of interaction • CM transformation • R matrix techniques to get f and d coefficients

  18. 7Be(p,g) Dean Halderson (2006)

  19. 15O levels www.tunl.duke.edu/nucldata

  20. 14N(p, ) level scheme Gamow peak at 26.5 keV for T6=15 figure taken from A. Formicola et al. (2004)

  21. The 15O positive parity spectrum

  22. S factor for the transition to the 3/2+ (6.79MeV) state in 15O

  23. 1/2+2 1/2- transition • Initial state • g.s.

  24. Total S factor

  25. Angular distribution and analyzing power

  26. Conclusions • Transition to 3/2+ agrees well with existing data • No significant contributions from subthreshold resonance • Low energy S factor is nearly flat • S(30) = 1.625 keVb

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