The muon, said Rabi, “who ordered that?” This page is an attempt at the receipt.
Unveiling the Mystery of Three Generations of Matter: Analyzing the Role of a Six-Index Calabi-Yau Manifold Across Space-Time
Every particle of substance arrives in exactly three copies — identical in every quality except mass. Nothing in the Standard Model says why.
χ = ±6, |χ|/2 = 3