期刊
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
卷 -, 期 3, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/1475-7516/2021/03/046
关键词
big bang nucleosynthesis; cosmological neutrinos; cosmological parameters from CMBR; particle physics - cosmology connection
资金
- DOE at the University of Minnesota [DE-SC0011842]
This study investigates the impact of new measurements of the d(p, gamma)He-3 cross section on Big Bang Nucleosynthesis (BBN), re-evaluating the thermal rate for the reaction and performing a likelihood analysis combining BBN and CMB data. The results show consistency between BBN theory, deuterium and He-4 observations, and the CMB when using the data-driven approach for reaction rates. Additionally, the new reaction data tightens constraints on the number of relativistic degrees of freedom during BBN.
We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements of the d(p, gamma)He-3 cross section by the LUNA Collaboration. These have an important effect on the primordial abundance of D/H which is also sensitive to the baryon density at the time of BBN. We have re-evaluated the thermal rate for this reaction, using a world average of cross section data, which we describe with model-independent polynomials; our results are in good agreement with a similar analysis by LUNA. We then perform a full likelihood analysis combining BBN and Planck cosmic microwave background (CMB) likelihood chains using the new rate combined with previous measurements and compare with the results using previous rates. Concordance between BBN and CMB measurements of the anisotropy spectrum using the old rates was excellent. The predicted deuterium abundance at the Planck value of the baryon density was (D/H)(BBN+CMB)(old) = (2.57 +/- 0.13) x 10(-5) which can be compared with the value determined from quasar absorption systems (D/H)(obs) = (2.55 +/- 0.03) x 10(-5). Using the new rates we find (D/H)(BBN+CMB) = (2.51 +/- 0.11) x 10(-5). We thus find consistency among BBN theory, deuterium and He-4 observations, and the CMB, when using reaction rates fit in our data-driven approach. We also find that the new reaction data tightens the constraints on the number of relativistic degrees of freedom during BBN, giving the effective number of light neutrino species N-nu = 2.880 +/- 0.144 in good agreement with the Standard Model of particle physics. Finally, we note that the observed deuterium abundance continues to be more precise than the BBN+CMB prediction, whose error budget is now dominated by d(d, n)He-3 and d(d, p)H-3. More broadly, it is clear that the details of the treatment of nuclear reactions and their uncertainty have become critical for BBN.
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