Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB (vol 01, 004, 2020)

Very recently, the LUNA collaboration has reported a new measurement of the d+p -> He-3+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.

Automated summary

The new measurement of the d+p -> He-3+gamma reaction rate has important implications for predicting the primordial deuterium abundance during the time of BBN, but has little impact on constraints on dark sector parameters. Constraints on neutrino-like particles are not significantly affected, while constraints on electrophilic dark sector states may vary moderately. With updated results for light dark sector states, the combination of BBN and CMB observations can lead to some variation in bounds on electrophilic dark sectors.