The "God particle" is a popular-science name for the Higgs boson. According to the theory of 1960's physicists François Englert, Robert Brout, and Peter Higgs, elementary particles such as protons and electrons have mass due to their interactions with the God particle. The experimental evidence behind the Higgs boson is extremely arduous; its existence wasn't confirmed until 2012... or so we thought.
Season 2 : episode 5
A chance discovery
In 1987, Claudia Tiedemann is reviewing data from a hushed incident at the Winden nuclear power plant from the previous year. She happens upon results that are irrefutable: There is evidence the God particle exists. It's a scientific sensation!
Claudia's predecessor Bernd Doppler cools her excitement. She can't both keep the accident a secret and share the discovery with the public. Claudia accepts this and continues doing her own research, even after the apocalypse in Winden.
She's getting more and more hopeful that she can find a way to make things right in Winden with her knowledge of the God particle. Could it be used to create a portal that allows time travel outside of the 33-year cycle?
Season 2 : episode 4
God in the restricted zone
In 2053, the God particle has become a mythical sensation. Hardly anyone knows or understands the scientific principles behind it, but that hasn't stopped people from deeming it their savior. It's rumored to be located in the ruins of Winden's nuclear power plant.
"You can't hide God. He doesn't belong to you alone." These are the final words of two men who are executed by the group led by Elisabeth Doppler in post-apocalyptic Winden. The men were trying to enter the restricted zone at the nuclear power plant.
There is a shapeless black mass in the nuclear reactor that can be used as a time portal under the right circumstances. When Silja discovers this and asks Elisabeth about it, she replies, "They say it's a piece of God. But in reality, it's a gateway to Hell."