Key points are not available for this paper at this time.
Recent precise determinations of the primordial He-abundance (Yₚ) from cosmic microwave background (CMB) analyses and cosmological nucleosynthesis computations, provide Yₚ=0. 2480. 001. On the other hand, recent works on the initial He-abundance of Galactic globular cluster (GGC) stars, making use of the R parameter as He-indicator, have consistently obtained Y₆₆₂0. 20. In light of this serious discrepancy that casts doubt on the adequacy of low mass He-burning stellar models, we have rederived the initial He-abundance for stars in two large samples of GGCs, by employing theoretical models computed using new and more accurate determinations of the Equation of State for the stellar matter, and of the uncertain ^12C (, ) ^16O reaction rate. Our models include semiconvection during the central convective He-burning phase, while the breathing pulses are suppressed, in agreement with the observational constraints coming from the measurements of the R₂ parameter in a sample of clusters. By taking into account the observational errors on the individual R-parameter values, as well as uncertainties in the GGC Fe/H scale, treatment of convection and ^12C (, ) ^16O reaction rate, we have obtained, respectively, a mean Y₆₆₂=0. 2430. 006 and Y₆₆₂=0. 2440. 006 for the two studied GGC samples. These estimates are now fully consistent with Yₚ obtained from CMB studies. Moreover, the trend of the individual He-abundances with respect to Fe/H is consistent with no appreciable He-enrichment along the GGC metallicity range.
Cassisi et al. (Sat,) studied this question.