Precise measurement of the Be 7 ( p , γ ) B 8 </…
2003; American Institute of Physics; Volume: 68; Issue: 6 Linguagem: Inglês
10.1103/physrevc.68.065803
ISSN1538-4497
AutoresA. Junghans, E. C. Mohrmann, K. A. Snover, T. D. Steiger, E. G. Adelberger, J. M. Casandjian, H. E. Swanson, L. Buchmann, S. H. Park, A. A. Zyuzin, A. M. Laird,
Tópico(s)Quantum Chromodynamics and Particle Interactions
ResumoWe present new measurements of the $^{7}\mathrm{Be}(p,\ensuremath{\gamma})^{8}\mathrm{B}$ cross section from ${\overline{E}}_{\text{c.m.}}=116$ to $2460\phantom{\rule{0.3em}{0ex}}\text{keV}$ (where c.m. means center-of-mass), which incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to ${S}_{17}(0)=22.1\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$ based on data from ${\overline{E}}_{\text{c.m.}}=116$ to $362\phantom{\rule{0.3em}{0ex}}\text{keV}$, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low-energy data. We compare our results to other ${S}_{17}(0)$ values extracted from both direct $[^{7}\mathrm{Be}(p,\ensuremath{\gamma})^{8}\mathrm{B}]$ and indirect (Coulomb-dissociation and heavy-ion reaction) measurements, and show that the results of these three types of experiments are not mutually compatible. We recommend a ``best'' value, ${S}_{17}(0)=21.4\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$, based on the mean of all modern direct measurements below the ${1}^{+}$ resonance. We also present $S$ factors at $20\phantom{\rule{0.3em}{0ex}}\text{keV}$ which is near the center of the Gamow window: the result of our measurements is ${S}_{17}(20)=21.4\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$, and the recommended value is ${S}_{17}(20)=20.6\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$.
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