在李政道教授所著的《粒子物理和场论导引》一书中,有一个很好的例证:1947年,鲍威尔从实验上明确区分出π介子和μ子,人们便开始了μ子衰变为电子加中微子(μ±→e±+两个中微子及反中微子)的电子能量谱形的研究。1950年,勒·密歇尔曾从理论上详细研究过这一谱形,指出这一谱形将依存于某一参量ρ,而ρ“是O与1”之间的任一实 There is a good example from Professor Li Zhengdao’s book, Guidance to Particle Physics and Field Theory: In 1947, Powell made a clear distinction between pion and muon experimentally, and muons began to decay For the electron plus neutrino (μ ± → e ± + two neutrino and anti-neutrino) electronic energy spectrum shape research. In 1950, Le Michel studied this spectrum theoretically in detail, pointing out that this spectrum will depend on some parameter ρ and ρ “any one between 0 and 1”