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Big Bang Nucleosynthesis results refined via the Trojan Horse Method

Roberta Spartà, Rosario Gianluca Pizzone, Livio Lamia, Alessandro Alberto Oliva, Marco La Cognata, Alessia Di Pietro, Pierpaolo Figuera, Giovanni Luca Guardo, Marco La Commara, Dario Lattuada, Marco Mazzocco, Sara Palmerini, Giuseppe Gabriele Rapisarda, Stefano Romano, Maria Letizia Sergi, Aurora Tumino

TL;DR

This work demonstrates how the Trojan Horse Method (THM) provides robust indirect measurements of low-energy nuclear cross sections relevant to Big Bang Nucleosynthesis (BBN) and integrates six THM-derived reaction rates into the PRIMAT BBN code. By substituting THM rates singly and collectively, the study reveals shifts in primordial abundances, notably a ~13% reduction in the total $^7$Li+Be abundance and a deuterium value of $\mathrm{D/H}\times10^{5}=2.61\pm0.13$, with $^4$He predicted as $Y_p=0.24699^{+0.00005}_{-0.00006}$, aligning better with observations in some channels. The Li-7 tension is alleviated, while $^6$Li, $^9$Be, and $^{11}$B predictions converge toward prior Coc2012 expectations, and CNO yields remain within the standard-BBN tail, potentially impacting Population III stellar evolution. Overall, THM provides a valuable, self-consistent avenue to refine BBN reaction rates and highlights the importance of further THM measurements to resolve remaining discrepancies such as the Cosmological Lithium Problem.

Abstract

This work presents the Trojan Horse Method (THM) as a powerful technique for measuring nuclear reaction cross sections at astrophysical energies. We then explore the impact of THM-derived reaction rates on the predictions of Standard Big Bang Nucleosynthesis (SBBN) using the PRIMAT code. Primordial abundances are shown for the single rate impact and, for the first time, also for all the THM rates together. The result shows significant differences with the use of THM rates, which in some cases goes in the direction of improving the agreement with the observations with respect to the use of only reaction rates from direct data, especially for the $^7$Li and deuterium abundances, which are still open issues for SBBN.

Big Bang Nucleosynthesis results refined via the Trojan Horse Method

TL;DR

This work demonstrates how the Trojan Horse Method (THM) provides robust indirect measurements of low-energy nuclear cross sections relevant to Big Bang Nucleosynthesis (BBN) and integrates six THM-derived reaction rates into the PRIMAT BBN code. By substituting THM rates singly and collectively, the study reveals shifts in primordial abundances, notably a ~13% reduction in the total Li+Be abundance and a deuterium value of , with He predicted as , aligning better with observations in some channels. The Li-7 tension is alleviated, while Li, Be, and B predictions converge toward prior Coc2012 expectations, and CNO yields remain within the standard-BBN tail, potentially impacting Population III stellar evolution. Overall, THM provides a valuable, self-consistent avenue to refine BBN reaction rates and highlights the importance of further THM measurements to resolve remaining discrepancies such as the Cosmological Lithium Problem.

Abstract

This work presents the Trojan Horse Method (THM) as a powerful technique for measuring nuclear reaction cross sections at astrophysical energies. We then explore the impact of THM-derived reaction rates on the predictions of Standard Big Bang Nucleosynthesis (SBBN) using the PRIMAT code. Primordial abundances are shown for the single rate impact and, for the first time, also for all the THM rates together. The result shows significant differences with the use of THM rates, which in some cases goes in the direction of improving the agreement with the observations with respect to the use of only reaction rates from direct data, especially for the Li and deuterium abundances, which are still open issues for SBBN.
Paper Structure (7 sections, 3 figures, 1 table)

This paper contains 7 sections, 3 figures, 1 table.

Table of Contents

  1. The Trojan Horse Method
  2. Using THM to shed light on BBN
  3. Adopted reaction rates
  4. Results
  5. Deuterium, $^{3,4}$Helium and $^{7}$Li primordial abundances
  6. $^6$Li, $^9$Be, $^{11}$B
  7. CNO

Figures (3)

  • Figure 1: Sketch of the mechanism to be investigated with THM. The $a$ nucleus breaks up in the two clusters $s$ and $x$, the spectator and the participant to the binary reaction of astrophysical interest with $A$, respectively.
  • Figure 2: The main reactions network for the SBBN model. The six out of the twelve measured with THM are indicated by green arrows.
  • Figure 3: BBN abundances resulting from PRIMAT with only direct data reaction rates (PRIMAT column of points), compared with the PRIMAT results using the THM rates of the six reactions measured (sec. \ref{['sec2']}) and all together (reverse triangles). Colored bands are the values of reference from observations (Y$_p$Aver, D/H Cooke,($^3$He+T)/H BalserBania in blue and Cooke2022 in red, ($^7$Li+$^7$Be)/H Sbordone2010.