Astrophysical implications of the proton-proton cross section updates

The p(p, e(+) v(e))H-2 reaction rate is an essential ingredient for theoretical computations of stellar models. In the past several values of the corresponding S-factor have been made available by different authors. Prompted by a recent evaluation of S(E), we analysed the effect of the adoption of different proton-proton reaction rates on stellar models, focusing, in particular, on the age of mid and old stellar clusters (1-12Gyr) and on standard solar model predictions. By comparing different widely adopted p(p, e(+) v(e))H-2 reaction rates, we found a maximum difference in the temperature regimes typical of main sequence hydrogen-burning stars (5 x 10(6)-3 x 10(7) K) of about 3%. Such a variation translates into a change of cluster age determination lower than 1%. A slightly larger effect is observed in the predicted solar neutrino fluxes with a maximum difference, in the worst case, of about 8%. Finally we also notice that the uncertainty evaluation of the present proton-proton rate is at the level of few parts per thousand, thus the p(p, e(+) v(e))H-2 reaction rate does not constitute anymore a significant uncertainty source in stellar models.