The nuclear physics input from the 3He( alpha , gamma )7Be cross section is a major uncertainty in the fluxes of 7Be and /sup 8neutrinos from the Sun predicted by solar models and in the sup 7/Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt- gamma technique and with inferior precision. Using a windowless gas target, high beam intensity, and low background gamma -counting facilities, the 3He( alpha , gamma )7Be cross section has been determined at 127, 148, and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He( alpha , gamma )7Be astrophysical S factor to solar energies.
Activation measurement of the 3He(alpha, gamma)7Be cross section at low energy / D. Bemmerer, F. Confortola, H. Costantini, A. Formicola, Gy. Gyurky, R. Bonetti, C. Broggini, P. Corvisiero, Z. Elekes, Zs. fulop, G. Gervino, A. Guglielmetti, C. Gustavino, G. Imbriani, M. Junker, M. Laubenstein, A. Lemut, B. Limata, V. Lozza, M. Marta, R. Menegazzo, P. Prati, V. Roca, C. Rolfs, C. Rossi Alvarez, E. Somorjai, O. Straniero, F. Strieder, F. Terrasi, H. P. Trautvetter. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 97:12(2006), pp. 122502.122502-1-122502.122502-5.
Activation measurement of the 3He(alpha, gamma)7Be cross section at low energy
R. Bonetti;A. Guglielmetti;
2006
Abstract
The nuclear physics input from the 3He( alpha , gamma )7Be cross section is a major uncertainty in the fluxes of 7Be and /sup 8neutrinos from the Sun predicted by solar models and in the sup 7/Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt- gamma technique and with inferior precision. Using a windowless gas target, high beam intensity, and low background gamma -counting facilities, the 3He( alpha , gamma )7Be cross section has been determined at 127, 148, and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He( alpha , gamma )7Be astrophysical S factor to solar energies.
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