Question: What American physicist discovered the positron which explained Chinese physicist Chung-Yao Chao's earlier experiments with gamma rays?
Sentence (from "Chung-Yao Chao"): Chung-Yao Chao studied the scattering of gamma rays in lead by pair production in 1930, without knowing that positrons were involved in the anomalously high scattering cross-section.
Relevant evidence: No