Astrophysical S factor for the {sup 15}N(p,{gamma}){sup 16}O reaction
- Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
- Universita di Catania and INFN Laboratori Nazionali del Sud, Catania (Italy)
- Nuclear Physics Institute, Czech Academy of Sciences, 250 68 Rez near Prague (Czech Republic)
The R-matrix approach has proved to be very useful in extrapolating the astrophysical factor down to astrophysically relevant energies, since the majority of measurements are not available in this region. However, such an approach has to be critically considered when no complete knowledge of the reaction model is available. To get reliable results in such cases one has to use all the available information from independent sources and, accordingly, fix or constrain variations of the parameters. In this paper we present a thorough R-matrix analysis of the {sup 15}N(p,{gamma}){sup 16}O reaction, which provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong J{sup {pi}}=1{sup -} resonances at E{sub R}=312 and 962 keV and direct capture to the ground state. Recently, a new measurement of the astrophysical factor for the {sup 15}N(p,{gamma}){sup 16}O reaction has been published [P. J. LeBlanc et al., Phys. Rev. C 82, 055804 (2010)]. The analysis has been done using the R-matrix approach with unconstrained variation of all parameters including the asymptotic normalization coefficient (ANC). The best fit has been obtained for the square of the ANC C{sup 2}=539.2 fm{sup -1}, which exceeds the previously measured value by a factor of {approx_equal}3. Here we present a new R-matrix analysis of the Notre Dame-LUNA data with the fixed within the experimental uncertainties square of the ANC C{sup 2}=200.34 fm{sup -1}. Rather than varying the ANC we add the contribution from a background resonance that effectively takes into account contributions from higher levels. Altogether we present ten fits, seven unconstrained and three constrained. For the unconstrained fit with the boundary condition B{sub c}=S{sub c}(E{sub 2}), where E{sub 2} is the energy of the second level, we get S(0)=39.0{+-}1.1 keVb and normalized {chi}-tilde{sup 2}=1.84, i.e., the result which is similar to LeBlanc et al. From all our fits we get the range 33.1{<=}S(0){<=}40.1 keVb which overlaps with the result of LeBlanc et al. We address also the physical interpretation of the fitting parameters.
- OSTI ID:
- 21499583
- Journal Information:
- Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 4 Vol. 83; ISSN 0556-2813; ISSN PRVCAN
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ASTROPHYSICS
ASYMPTOTIC SOLUTIONS
BARYON REACTIONS
BOUNDARY CONDITIONS
CAPTURE
CARBON COMPOUNDS
CARBON NITRIDES
CHARGED-PARTICLE REACTIONS
DECAY
ENERGY RANGE
EVEN-EVEN NUCLEI
GAMMA DECAY
HADRON REACTIONS
ISOTOPES
KEV RANGE
LIGHT NUCLEI
MATHEMATICAL SOLUTIONS
MATRICES
NITRIDES
NITROGEN 15 TARGET
NITROGEN COMPOUNDS
NUCLEAR DECAY
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
OXYGEN 16
OXYGEN ISOTOPES
PHYSICS
PNICTIDES
PROTON REACTIONS
R MATRIX
RESONANCE
STABLE ISOTOPES
TARGETS