Astrophysical implications of the proton–proton cross section updates

The p(p,e+νe)H2 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)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 (1–12 Gyr) and on standard solar model predictions. By comparing different widely adopted p(p,e+νe)H2 reaction rates, we found a maximum difference in the temperature regimes typical of main sequence hydrogen-burning stars (5×106–3×107 K5×106–3×107 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 ‰, thus the p(p,e+νe)H2 reaction rate does not constitute anymore a significant uncertainty source in stellar models.