We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8 B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.

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We present new measurements of the 7 Be(p,γ) 8 B cross section fromĒcm = 116 to 2460 keV, that incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to S17(0) = 22.1 ± 0.6(expt) ± 0.6(theor) eV b based on data from Ecm = 116 to 362 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 S17(0) values extracted from both direct ( 7 Be(p,γ) 8 B) and indirect (Coulomb dissociation and heavy-ion reaction) measurements, and show that the results of these 3 types of experiments are not mutually compatible. We recommend a "best" value, S17(0) = 21.4 ± 0.5(expt) ± 0.6(theor) eV b, based on the mean of all modern direct measurements below the 1 + resonance. We also present S-factors at 20 keV which is near the center of the Gamow window: the result of our measurements is S17(20) = 21.4 ± 0.6(expt) ± 0.6(theor) eV b, and the recommended value is S17(20) = 20.7 ± 0.5(expt) ± 0.6(theor) eV b.PACS numbers: 26.20+f, 26.65+t, 25.40Lw

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The dipole response of the N = 50 nucleus 90 Zr was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 7.9, 9.0, and 13.2 MeV. We identified 189 levels up to an excitation energy of 12.9 MeV. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we derived the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (γ, n) data and thus provides information about the extension of the dipole-strength distribution toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range of 6 MeV to 11 MeV. Calculations within the framework of the quasiparticle-phonon model ascribe this strength to a vibration of the excessive neutrons against the N = Z neutron-proton core, giving rise to a pygmy dipole resonance.