Critical assessment of the claim of a significant difference between the results of measurements of the Coulomb dissociation ofB8and theBe7(p,γ)B8direct capture reaction

Abstract

The Coulomb dissociation (CD) of $^{8}\mathrm{B}$ has emerged as a landmark testing ground of the very method of CD for measuring the cross section of the low-energy $^{7}\mathrm{Be}$($p,\ensuremath{\gamma}$)$^{8}\mathrm{B}$ direct capture (DC) reaction. Recent claims of evidence of slope difference between CD and DC results are critically examined. We include all relevant RIKEN2 data and all previously published DC data, and we examine the extracted so-called average scale-independent slope ($b$). The parametrization used by the Seattle group to extract the so-called $b$-slope parameter is also examined at energies above 300 keV. Considering the physical slope (${S}^{'}=\mathit{dS}/\mathit{dE}$) above 300 keV, we observe a ($1.7\ensuremath{\sigma}$) agreement between slopes (${S}^{'}$) measured in CD and DC above 300 keV. The claim that ${S}_{17}(0)$ values extracted from CD data are inconsistent and lower than DC results arises from a neglect of substantial systematic uncertainty of low-energy CD data. A consideration of the published CD ${S}_{17}(0)$ results yields very consistent ${S}_{17}(0)$ values that agree with most recent DC measurements. The recent correction of the $b$-slope parameter suggested by Esbensen, Bertsch, and Snover (EBS) was applied to the wrong $b$ slope calculated using part of the RIKEN2 data. When the correct slope of the RIKEN2 data is used, the EBS correction in fact leads to a substantial disagreement between the slopes of the RIKEN2 data and DC data. In spite of an agreement between CD and DC data neither allow for extracting the slope above 300 keV with high accuracy. Uncertainty of the slope (${S}^{'}$) leads to an additional uncertainty of the extrapolated ${S}_{17}(0)$. The slope of the astrophysical cross-section factor ${S}_{17}$ must be measured with high precision to enable extraction of the $d/s$ ratio and a high-precision extrapolation of ${S}_{17}(0)$.