Model independent predictions of big bang nucleosynthesis from He and Li: consistency and implications

Abstract

We examine in detail how BBN theory is constrained, and what predictions it can make, when using only the most model-independent observational constraints. We avoid the uncertainties and model-dependencies that necessarily arise when solar neighborhood D and 3 He abundances are used to infer primordial D and 3 He via chemical and stellar evolution models. Instead, we use 4 He and 7 Li, thoroughly examining the effects of possible systematic errors in each. Via a likelihood analysis, we find near perfect agreement between BBN theory and the most model-independent data. Given this agreement, we then assume the correctness of BBN to set limits on the single parameter of standard BBN, the baryon-to-photon ratio, and to predict the primordial D and 3 He abundances. We also repeat our analysis including recent measurements of D/H from quasar absorption systems and find that the near perfect agreement between theory and observation of the three isotopes, D, 4 He and 7 Li is maintained. These results have strong implications for the chemical and stellar evolution of the light elements, in particular for 3 He. In addition, our results (especially if the D/H measurements are confirmed) have implications for the stellar depletion of 7 Li. Finally, we set limits on the number N ν of neutrino flavors, using an analysis which carefully and systematically includes all available experimental constraints. The value N ν = 3.0 fits best with BBN and a 95% CL upper limit of N ν < ∼ 4 is established.

Primordial nucleosynthesis and hadronic decay of a massive particle with a relatively short lifetime

“…Here we have added the additional uncertainty for fear that the 7 Li in halo stars might have been supplemented (by production in cosmic-ray interactions) or depleted (in stars) [16]. 2…”

Inhomogeneous big-bang nucleosynthesis in light of recent observations

“…In SBBN these constraints lead to a baryon density i n the narrow range 10 In our third set we consider the case for low in SBBN [13]. (See Fig.…”

A big band nucleosynthesis likelihood analysis of the baryon-to-photon ratio and the number of light particle degrees of freedom

“…For these reasons it was argued [7,8] that the analysis comparing BBN theory and observations should be based primarily on the two isotopes which are the least sensitive to the effects of evolution, namely, 4 He and 7 Li. In [8], the baryon-to-photon ratio, η was determined on the basis of a likelihood analysis using 4 He and 7 Li. Because of the monotonic dependence of 4 He on η, the 4 He likelihood distribution has a single (but relatively broad) peak at η 10 = 1.75.…”

“…When D/H from quasar absorption systems (those showing a high value for D/H [22]) is included in the analysis this range is cut to 1.50 < η 10 < 2.55. In [8], the range in η from the likelihood analysis was translated into a range for N ν . Because of the agreement between the likelihood predictions of 4 He and 7 Li for N ν = 3, the best fit value was found to be very close to N ν = 3.…”