Chung-Yao Chao (; 27 June 1902 – 28 May 1998) was a Chinese theoretical physicist. He studied the scattering of

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

s in lead by

pair production Pair production is the creation of a subatomic particle and its antiparticle from a neutral boson. Examples include creating an electron and a positron, a muon and an antimuon, or a proton and an antiproton. Pair production often refers ...

in 1930, without knowing that

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

s were involved in the anomalously high scattering cross-section. When the positron was discovered by

Carl David Anderson Carl David Anderson (September 3, 1905 – January 11, 1991) was an American particle physicist who shared the 1936 Nobel Prize in Physics with Victor Francis Hess for his discovery of the positron. Biography Anderson was born in New York Cit ...

in 1932, confirming the existence of

Paul Dirac Paul Adrien Maurice Dirac ( ; 8 August 1902 – 20 October 1984) was an English mathematician and Theoretical physics, theoretical physicist who is considered to be one of the founders of quantum mechanics. Dirac laid the foundations for bot ...

's "

antimatter In modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding subatomic particle, particles in "ordinary" matter, and can be thought of as matter with reversed charge and parity, or go ...

", it became clear that positrons could explain Chung-Yao Chao's earlier experiments, with the gamma rays being emitted from electron-positron annihilation. He entered Nanjing Higher Normal School (later renamed National Southeastern University, National Central University and

Nanjing University Nanjing University (NJU) is a public university in Nanjing, Jiangsu, China. It is affiliated and sponsored by the Ministry of Education. The university is part of Project 211, Project 985, and the Double First-Class Construction. The univers ...

), in 1920 and earned a BS in

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

in 1925. Then he earned a

PhD A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...

degree in physics under supervision of Nobel Prize laureate

Robert Andrews Millikan Robert Andrews Millikan ( ; March 22, 1868 – December 19, 1953) was an American physicist who received the Nobel Prize in Physics in 1923 "for his work on the elementary charge of electricity and on the photoelectric effect". Millikan gradua ...

California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...

in 1930. Later he went back to China and joined the physics faculty of

Tsinghua University Tsinghua University (THU) is a public university in Haidian, Beijing, China. It is affiliated with and funded by the Ministry of Education of China. The university is part of Project 211, Project 985, and the Double First-Class Constructio ...

Beijing Beijing, Chinese postal romanization, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's List of national capitals by population, most populous national capital city as well as ...

Nobel Prize controversy

The 1936

Nobel Prize for Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prize, Nobel Prizes establi ...

went to Carl D. Anderson for the discovery of the positron. While a graduate student at Caltech in 1930, Chao was the first to experimentally identify

s through

electron–positron annihilation Electron–positron annihilation occurs when an electron () and a positron (, the electron's antiparticle) collide. At low energies, the result of the collision is the annihilation of the electron and positron, and the creation of energetic ph ...

, but did not realize what they were. Anderson, Chao's classmate at Caltech, used the same

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

source, , as Chao. (Historically, was known as "thorium C double prime" or "ThC", see

decay chain In nuclear science a decay chain refers to the predictable series of radioactive disintegrations undergone by the nuclei of certain unstable chemical elements. Radioactive isotopes do not usually decay directly to stable isotopes, but rather ...

s.) Fifty years later, Anderson admitted that Chao had inspired his discovery: Chao's research formed the foundation from which much of Anderson's own work developed. Chao died in 1998, without sharing in a Nobel Prize acknowledgment.

Nobel Prize controversy

References

Further reading