TY - JOUR

T1 - The impact of new d(p,γ)3 rates on Big Bang Nucleosynthesis

AU - Yeh, Tsung Han

AU - Olive, Keith A.

AU - Fields, Brian D.

N1 - Funding Information:
The work of K.A.O. was supported in part by DOE grant DE-SC0011842 at the University of Minnesota.
Publisher Copyright:
© 2021 Institute of Physics Publishing. All rights reserved.

PY - 2021/3

Y1 - 2021/3

N2 - We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements of the d(p, )3He 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)old BBN+CMB = (2.57 ± 0.13) × 10-5 which can be compared with the value determined from quasar absorption systems (D/H)obs = (2.55 ± 0.03) × 10-5. Using the new rates we find (D/H)BBN+CMB = (2.51 ± 0.11) × 10-5. We thus find consistency among BBN theory, deuterium and 4He 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 Nν= 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)3He and d(d, p)3H. More broadly, it is clear that the details of the treatment of nuclear reactions and their uncertainty have become critical for BBN.

AB - We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements of the d(p, )3He 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)old BBN+CMB = (2.57 ± 0.13) × 10-5 which can be compared with the value determined from quasar absorption systems (D/H)obs = (2.55 ± 0.03) × 10-5. Using the new rates we find (D/H)BBN+CMB = (2.51 ± 0.11) × 10-5. We thus find consistency among BBN theory, deuterium and 4He 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 Nν= 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)3He and d(d, p)3H. More broadly, it is clear that the details of the treatment of nuclear reactions and their uncertainty have become critical for BBN.

KW - Big bang nucleosynthesis

KW - Cosmological neutrinos

KW - Cosmological parameters from CMBR

KW - Particle physics - cosmology connection

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U2 - 10.1088/1475-7516/2021/03/046

DO - 10.1088/1475-7516/2021/03/046

M3 - Article

AN - SCOPUS:85103481908

VL - 2021

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 3

ER -