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Title: Low energy scattering cross section ratios of N 14 ( p , p ) N 14

Journal Article · · Physical Review C, Nuclear Physics
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2];  [2];  [3]
  1. Univ. of Notre Dame, IN (United States). Joint Inst. for Nuclear Astrophysics
  2. Univ. of North Carolina, Chapel Hill, NC (United States); Triangle Universities Nuclear Lab., Durham, NC (United States)
  3. Ball State Univ., Muncie, IN (United States)

Background: The slowest reaction in the first CNO cycle is 14N(p, γ) 15O, therefore its rate determines the overall energy production efficiency of the entire cycle. The cross section presents several strong resonance contributions, especially for the ground-state transition. Some of the properties of the corresponding levels in the 15O compound nucleus remain uncertain, which affects the uncertainty in extrapolating the capture cross section to the low energy range of astrophysical interest. Purpose: The 14N (p, γ) 15O cross section can be described by using the phenomenological R matrix. Over the energy range of interest, only the proton and γ-ray channels are open. Since resonance capture makes significant contributions to the 14N (p, γ) 15O cross section, resonant proton scattering data can be used to provide additional constraints on the R-matrix fit of the capture data. Methods: A 4 MV KN Van de Graaff accelerator was used to bombard protons onto a windowless gas target containing enriched 14N gas over the proton energy range from Ep =1.0 to 3.0 MeV. Scattered protons were detected at θlab = 90,120°,135 °,150°, and 160° using ruggedized silicon detectors. In addition, a 10 MV FN Tandem Van de Graaff accelerator was used to accelerate protons onto a solid Adenine ( C 5 H 5 N 5 ) target, of natural isotopic abundance, evaporated onto a thin self-supporting carbon backing, over the energy range from E p = 1.8 to 4.0 MeV. Scattered protons were detected at 28 angles between θ lab = 30. 4° and 167. 7° by using silicon photodiode detectors. Results: Relative cross sections were extracted from both measurements. While the relative cross sections do not provide as much constraint as absolute measurements, they greatly reduce the dependence of the data on otherwise significant systematic uncertainties, which are more difficult to quantify. The data are fit simultaneously using an R-matrix analysis and level energies and proton widths are extracted. Even with relative measurements, the statistics and large angular coverage of the measurements result in more confident values for the energies and proton widths of several levels; in particular, the broad resonance at Ec.m. = 2.21 MeV, which corresponds to the 3/2+ level at Ex = 9.51 MeV in 15O. In particular, the s - and d -wave angular-momentum channels are separated. Conclusion: The relative cross sections provide a consistent set of data that can be used to better constrain a full multichannel R-matrix extrapolation of the capture data. It has been demonstrated how the scattering data reduce the uncertainty through a preliminary Monte Carlo uncertainty analysis, but several other issues remain that make large contributions to the uncertainty, which must be addressed by further capture and lifetime measurements.

Research Organization:
University of North Carolina, Chapel Hill, NC (United States); Duke Univ., Durham, NC (United States). Triangle Universities Nuclear Laboratory
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
FG02-97ER41041
OSTI ID:
1600481
Alternate ID(s):
OSTI ID: 1178478
Journal Information:
Physical Review C, Nuclear Physics, Vol. 91, Issue 4; ISSN 0556-2813
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 11 works
Citation information provided by
Web of Science

References (27)

R-Matrix Theory of Nuclear Reactions journal April 1958
Age Estimates of Globular Clusters in the Milky Way: Constraints on Cosmology journal January 2003
Asymptotic normalization coefficients for 14 N + p 15 O and the astrophysical S factor for 14 N ( p , γ ) 15 O journal June 2003
Measurement of elastic C 12 + α scattering: Details of the experiment, analysis, and discussion of phase shifts journal May 2009
The R -matrix theory journal February 2010
Evaluation of non-Rutherford proton elastic scattering cross section for nitrogen journal April 2008
Helium burning of22Ne journal December 1989
S-factor of 14N(p,γ)15O at astrophysical energies⋆ journal September 2005
The 14N(p,)15O low-energy -factor journal July 2001
Solar Neutrinos: Status and Prospects journal August 2013
Stellar reaction rate of 14N(p, γ)15O and hydrogen burning in massive stars journal June 1987
Energy levels of light nuclei A = 13–15 journal February 1991
Measurement of elastic 12 C + α scattering: Above the proton separation energy journal April 2012
Alternative parametrization of R -matrix theory journal October 2002
Connection between asymptotic normalization coefficients, subthreshold bound states, and resonances journal June 1999
Solar fusion cross sections. II. The p p chain and CNO cycles journal April 2011
Minuit - a system for function minimization and analysis of the parameter errors and correlations journal December 1975
Low-energy-threshold analysis of the Phase I and Phase II data sets of the Sudbury Neutrino Observatory journal May 2010
Direct Measurement of the N 14 ( p , γ ) O 15 S Factor journal March 2005
Lifetime of the 6793-keV State in O 15 journal September 2001
Lifetime measurement of the 6792 keV state in O 15 , important for the astrophysical S factor extrapolation in N 14 ( p , γ ) O 15 journal May 2008
N 22 e ( α , n ) M 25 g : The Key Neutron Source in Massive Stars journal October 2001
E1 strength of the subthreshold 3/2+ state in 15O studied by Coulomb excitation journal January 2004
14 N ( 3 He , d ) 15 O as a probe of direct capture in the 14 N ( p , γ ) 15 O reaction journal November 2002
Monte Carlo uncertainty of the He 3 ( α , γ ) Be 7 reaction rate journal September 2014
AZURE: An R -matrix code for nuclear astrophysics journal April 2010
Precision Measurement of the Be 7 Solar Neutrino Interaction Rate in Borexino journal September 2011

Cited By (2)

New investigations of the 10 B(p,${\alpha }_{0}$) 7 Be reaction at bombarding energies between 0.6 and 1 MeV journal February 2016
Experimental studies of clustering in light nuclei: 11,12,13,16C journal January 2020

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