Addendum: Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB

TL;DR

This paper updates bounds on MeV-scale dark sectors using recent BBN and CMB data, showing that some constraints remain stable while others vary with new reaction rate measurements.

Contribution

It provides refined constraints on light dark sector particles considering recent experimental updates, extending previous analyses with new reaction rate data.

Findings

BBN-only and Planck-only bounds remain stable.

Constraints on neutrinophilic particles are unaffected.

Electrophilic dark sector bounds can vary moderately.

Abstract

Very recently, the LUNA collaboration has reported a new measurement of the $d+p\to {}^{3}\text{He}+\gamma$ reaction rate, which plays an important role in the prediction of the primordial deuterium abundance at the time of BBN. This new measurement has triggered a new set of global BBN analyses within the context of the Standard Model. In this addendum to JCAP 01 (2020) 004 (arXiv:1910.01649), we consider the implications of these new results for our constraints on MeV-scale dark sectors. Importantly, we find that our bounds in the BBN-only and Planck-only analyses are insensitive to these updates. Similarly, we find that our constraints derived using BBN and CMB data simultaneously are not significantly modified for neutrinophilic particles. The bounds on electrophilic dark sector states, however, can vary moderately when combining BBN and CMB observations. We present updated results for all the relevant light dark sector states, calculated using the rates obtained by the leading groups performing standard BBN analyses.