Feasibility of s‑Channel Higgs Formation at an e+e− Collider

Ascertain whether an electron–positron collider can achieve the requisite beam‑energy spread and luminosity to observe s‑channel Higgs formation (e+e− → H), enabling direct Higgs line‑shape measurements and potentially accessing the H → e+e− coupling.

Background

Direct paper of the Higgs line shape and the ultra‑rare H → e+e− coupling would be transformative but requires s‑channel production in e+e− collisions with extraordinarily narrow energy spread. The paper notes that while FCC‑ee proponents are hopeful, feasibility is not established.

Demonstrating feasibility would define concrete machine performance targets and clarify the physics reach of proposed Higgs factories.