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出典:『Wikipedia』 (2011/07/08 22:49 UTC 版)

英語による解説

引用

Nucleon spin structure describes the partonic structure of nucleon (proton and neutron) intrinsic angular momentum (spin). The key question is how nucleon spin 1/2 is carried by its constituents, say partons (quarks and gluons). It was originally expected before the 1980s that quarks carry all of the nucleon spin, but later experiments contradict this expectation. In the late 1980s, the European Muon Collaboration conducted experiments that suggested the spin carried by quarks is not sufficient to justify the total spin of the nucleons. This problem of where the missing spin lies is sometimes referred to as the proton spin crisis.