Aver et al. in [2601.22238] have recently performed an impressive new analysis that resulted in a 0.5% determination of the primordial helium abundance. The primordial helium abundance is a key probe of the early Universe and tells us how fast the Universe was expanding about a second after the Big Bang.
In light of these exciting new results we organize a EuCAPT Fast Response workshop on the topic. The idea is to hear about these new results and discuss their methodology as well as their implications for searches for beyond the Standard Model physics, including new relativistic species contributing to Neff.
The event will be fully online and will take place over zoom on Thursday April 23, 2026, 15:30-17:00 CET.
The agenda is as follows:
15:30-15:35 -- Welcome
15:35-16:15 -- Erik Aver: "A New Value of the Primordial Helium Abundance"
16:15-17:00 -- Panel discussion: Ryan Cooke, Cara Giovanetti, Elena Terlevich, Oleg Kurichin, Kuldeep Verma.
We welcome the worldwide astroparticle theory and cosmology community to join the event. There will be plenty of time for discussions and questions, also from online participants.
Anyone can join the event by clicking on the Videoconference tab.
