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7Be(p,gamma)8B astrophysical S factor from precision cross section measurements
A R Junghans1, E C Mohrmann, K A Snover
1Center for Experimental Nuclear Physics and Astrophysics, University of Washington, Seattle, Washington 98195, USA.
Physical Review Letters
|January 22, 2002
Summary
This study precisely measured the 7Be(p,gamma)8B reaction cross section, crucial for understanding solar fusion. The findings yield an improved value for the S17(0) astrophysical S-factor, vital for solar neutrino models.
Area of Science:
- Nuclear Astrophysics
- Particle Physics
- Stellar Evolution
Background:
- The 7Be(p,gamma)8B reaction is a key process in the proton-proton chain of nuclear fusion in stars.
- Accurate cross-section data is essential for understanding solar neutrino production and stellar models.
Purpose of the Study:
- To precisely measure the 7Be(p,gamma)8B reaction cross section over a range of center-of-mass energies.
- To determine the astrophysical S-factor S17(0) with high accuracy.
Main Methods:
- Experimental measurement of the 7Be(p,gamma)8B cross section from 186 to 1200 keV.
- Careful accounting for all significant systematic errors, including 8B backscattering losses.
- Analysis combined with theoretical calculations from Descouvemont and Baye.
Main Results:
- Achieved a statistical-plus-systematic precision better than +/-5% per data point.
- Obtained S17(0) = 22.3+/-0.7(expt)+/-0.5(theor) eV b using data below 300 keV.
Conclusions:
- The precise cross-section measurements provide a refined value for the S17(0) astrophysical S-factor.
- This improved S17(0) value will enhance the accuracy of solar neutrino predictions and models of stellar nucleosynthesis.