s -wave scattering lengths for the Be7+p system from an R -matrix analysis

Abstract

The astrophysical S-factor for the radiative proton capture reaction on 7 Be (S17) at low energies is affected by the s-wave scattering lengths. We report the measurement of elastic and inelastic scattering cross sections for the 7 Be+p system in the center-of-mass energy range 0.474-2.740 MeV and center-of-mass angular range 70 • -150 • . A radioactive 7 Be beam produced at Oak Ridge National Laboratory's (ORNL) Holifield Radioactive Ion Beam Facility was accelerated and bombarded a thin polypropylene (CH2)n target. Scattered ions were detected in the segmented Silicon Detector Array. Using an R-matrix analysis of ORNL and Louvain-la-Neuve cross-section data, the s-wave scattering lengths for channel spins 1 and 2 were determined to be 17.34 +1.11 −1.33 and -3.18 +0.55 −0.50 fm, respectively. The uncertainty in the s-wave scattering lengths reported in this work is smaller by a factor of 5-8 compared to the previous measurement, which may reduce the overall uncertainty in S17 at zero energy. The level structure of 8 B is discussed based upon the results from this work. Evidence for the existence of 0 + and 2 + levels in 8 B at 1.9 and 2.21 MeV, respectively, is observed.

Ab Initio Nuclear Reaction Theory with Applications to Astrophysics

“…Unlike the NCSM/RGM calculations [159], the NCSMC S-wave phase shifts shown in the left panel of Fig. 14 manifest consistent scattering length signs with those determined in recent measurements (negative for 5 S 2 , positive for 3 S 1 ) [161]. The calculated astrophysical S factor shown in the right panel of Fig.…”

Structure of C9 through proton resonance scattering with the Texas Active Target detector

“…12). For the 7 Be+p the most recent comprehensive R-matrix analysis [34] gives -3.18 +0.55 −0.50 fm scattering length for the = 0 2 − partial wave. The potential model = 0 phase shift for the 7 Be+p scattering calculated using parameters given in the caption for Fig.…”