# Revised Uncertainties in Big Bang Nucleosynthesis

## TL;DR

This paper updates the uncertainties and constraints of primordial light element abundances in Big Bang Nucleosynthesis using revised reaction rates and a Monte Carlo approach, providing new bounds on cosmological parameters.

## Contribution

It introduces a modified BBN code with updated reaction rates and performs a Monte Carlo analysis to refine abundance constraints and neutrino number bounds.

## Key findings

- New 2σ constraints on D, 3He, 4He, and 7Li abundances.
- Updated reaction rates from NACRE, REACLIB, and R-Matrix.
- Derived a new limit on the effective number of neutrinos.

## Abstract

Big Bang Nucleosynthesis (BBN) explores the first few minutes of nuclei formation after the Big Bang. We present updates that result in new constraints at the 2{\sigma} level for the abundances of the four primary light nuclides - D,3He,4He, and 7Li - in BBN. A modified standard BBN code was used in a Monte Carlo analysis of the nucleosynthesis uncertainty as a function of baryon-to-photon ratio. Reaction rates were updated to those of NACRE and REACLIB, and R-Matrix calculations. The results are then used to derive a new constraint on the effective number of neutrinos.