Measurement of d+^{7}Be Cross Sections for Big-Bang Nucleosynthesis

Area of Science:

• Nuclear astrophysics
• Particle physics
• Cosmology

Background:

• The primordial lithium problem, a discrepancy between predicted and observed abundances of lithium-7 in the early universe, remains a significant puzzle in big-bang nucleosynthesis.
• Understanding the production and destruction mechanisms of mass-7 nuclides, particularly beryllium-7, is crucial for resolving this cosmological issue.

Purpose of the Study:

• To experimentally determine the nuclear reaction cross sections for ^{7}Be + deuterium.
• To investigate the role of the ^{7}Be + d reaction, specifically the (d,α) channel, in the production of mass-7 nuclides.
• To assess the impact of newly measured cross sections and resonances on big-bang nucleosynthesis calculations and the primordial lithium problem.

Main Methods:

• Measurement of ^{7}Be + deuterium reaction cross sections at center-of-mass energies from 0.2 to 1.5 MeV.
• Focus on the (d,α) reaction channel, which was less constrained in previous studies.
• Identification and characterization of nuclear resonances within the relevant Gamow window for big-bang nucleosynthesis.

Main Results:

• The measured cross sections are primarily driven by the (d,α) reaction channel.
• A new resonance was observed at 0.36(5) MeV with a strength of ωγ=1.7(5) keV, located within the Gamow window.
• Calculations incorporating the new experimental data indicate a reduction in the predicted primordial ^{7}Li abundance.

Conclusions:

• The ^{7}Be + deuterium reaction, particularly the newly identified resonance, influences the production of primordial ^{7}Li.
• While the observed resonance affects the predicted abundance of lithium-7, it does not fully resolve the long-standing primordial lithium problem.
• Further research into other nucleosynthesis pathways and potential solutions to the lithium problem is warranted.