High-Precision Measurement of D(${\hat{I}}^3$, $n$)$p$ Photodisintegration Reaction and Implications for Big-Bang Nucleosynthesis

Abstract

We report on a high-precision measurement of the D(${\hat{I}}^3$,\,$n$)$p$ photodisintegration reaction at the newly commissioned Shanghai Laser Electron Gamma Source (SLEGS), employing a quasi-monochromatic ${\hat{I}}^3$-ray beam from Laser Compton Scattering. The cross sections were determined over $E_{\hat{I}}^3$=2.327--7.089 MeV, achieving up to a factor of 2.2 improvement in precision near the neutron separation threshold. Combined with previous data in a global Markov chain Monte Carlo (MCMC) analysis using dibaryon effective field theory, we obtained the unprecedentedly precise $p$($n$,\,${\hat{I}}^3$)D cross sections and thermonuclear rate, with a precision up to $\approx$4 times higher than previous evaluations. Implemented in a standard Big-Bang Nucleosynthesis (BBN) framework, this new rate decreases uncertainty of the key cosmological parameter of baryon density $\hat{I}{\text{c◯}}_b{h}^2$ by up to $\approx$16\% relative to the LUNA result. A residual $\approx$1.2$\ddot{I}ƒ$ tension between $\hat{I}{\text{c◯}}_b{h}^2$ constrained from primordial D/H observations and CMB measurements persists, highlighting the need for improved $dd$ reaction rates and offering potential hints of new physics beyond the standard model of cosmology.

Cited by in corpus (1)

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