Big Bang Nucleosynthesis and Particle Dark Matter (0906.2087v1)

Abstract: We review how our current understanding of the light element synthesis during the Big Bang Nucleosynthesis era may help shed light on the identity of particle dark matter.

• The paper demonstrates how Big Bang Nucleosynthesis processes constrain dark matter properties, emphasizing catalyzed BBN and residual annihilation effects.
• It employs observational light element abundances and theoretical predictions to address discrepancies like the lithium problem.
• Findings imply that non-thermal dark matter interactions during nucleosynthesis may reveal new physics in cosmology.

Analyzing Big Bang Nucleosynthesis and its Connection to Particle Dark Matter

Jedamzik and Pospelov's paper "Big Bang Nucleosynthesis and Particle Dark Matter" provides a detailed investigation of how the nucleosynthesis processes during the early universe can inform our understanding of dark matter particle identity. This essay will offer an expert analysis of the authors' approach, their findings, and the implications for cosmological models and particle physics.

Big Bang Nucleosynthesis Overview

Big Bang Nucleosynthesis (BBN) represents a critical epoch in the universe's early history during which the synthesis of light elements occurred. Beginning approximately one second and lasting a few minutes post-Big Bang, temperatures were conducive for nuclear reactions involving protons and neutrons, leading to the formation of elements such as helium ($^{4}$He), deuterium ($^{2}$H), and trace amounts of lithium ($^{7}$Li) and beryllium ($^{9}$Be).

Constraints and Observations on Light Element Abundances

BBN predictions align closely with observed abundances of light elements. Baryon-to-photon ratio $\eta$, inferred from observations such as CMB anisotropies, plays a pivotal role in these predictions. However, discrepancies continue to exist, notably with lithium, referred to as the "lithium problem," where observed primordial abundances differ markedly from theoretical predictions. This discrepancy may hint at non-standard physics or unaccounted stellar processing.

Implications for Particle Dark Matter

The paper bridges BBN with dark matter theories, emphasizing BBN's potential to constrain dark matter properties or suggest new physics. Notably, Jedamzik and Pospelov explore the effects of non-thermal processes, such as the annihilation or decay of hypothetical dark matter during BBN, altering standard nucleosynthesis outcomes. Additional "degrees of freedom" or exotic scenarios such as supersymmetric particles during BBN can markedly shift predictions on elemental abundances.

Catalyzed BBN (CBBN)

A focal point of the paper is CBBN, where hypothetical negatively charged particles could catalyze nuclear reactions. This process involves forming bound states with nuclei, modifying reaction pathways, and possibly producing elements previously suppressed under SBBN conditions. The authors highlight the potential for CBBN to resolve discrepancies like the lithium problem, providing a framework for particles like staus (supersymmetric partners) influencing nuclear reactions during BBN.

Residual Dark Matter Annihilation

The analysis also includes residual dark matter annihilation and its role during BBN. Jedamzik and Pospelov explore scenarios where annihilating dark matter particles can account for observed lithium abundances, showing how annihilation rates impact nucleosynthesis outcomes. Specifically, they provide limits on annihilation cross-sections that align with both lithium and deuterium observations and constraints.

Future Prospects and Theoretical Implications

The paper posits BBN as a potent probe for dark matter properties, suggesting that persistent discrepancies or unobserved excesses hint at novel physics or undiscovered processes. Continued observational efforts on primordial light element abundances alongside advancements in accelerators and detectors will be crucial for refining these constraints and potentially discovering new particle physics models.

Conclusion

Jedamzik and Pospelov's examination of BBN and particle dark matter offers substantial insights into cosmological and particle physics intersections, providing a significant analytical framework for ongoing research in understanding dark matter's nature. As our observational and theoretical capabilities progress, BBN will remain an invaluable tool in deciphering cosmic evolution and the fundamental constituents of our universe.