Proton spin crisis - Wikipedia
The proton spin crisis (or proton spin puzzle) is a theoretical crisis precipitated by a 1987 experiment by the European Muon Collaboration (EMC), [1] which tried to determine the distribution of spin within the proton. [2] Physicists expected …
The spin of a proton – Physics World
2015年6月4日 · Spin is a quantum-mechanical property, akin to the angular momentum of a classical sphere rotating on its axis, except it comes in discrete units of integer or half-integer multiples of ħ. The proton, like the electron and neutron, has a spin of ħ /2, or “spin-1/2”. So do each of its three quarks.
Spin (physics) - Wikipedia
Spin is described mathematically as a vector for some particles such as photons, and as a spinor or bispinor for other particles such as electrons. Spinors and bispinors behave similarly to vectors: they have definite magnitudes and change under rotations; however, they …
What we know and what we don’t know about the proton spin …
2020年11月23日 · There are two established approaches to look at the composition of the proton spin: the frame-independent spin structure (or the Ji sum rule) and the infinite-momentum-frame or parton spin...
質子自旋危機 - 维基百科，自由的百科全书
質子自旋危機 （英語： Proton spin crisis），有時稱作「質子自旋之謎」，是1987年的一次實驗促成的理論危機，該實驗試著測定 質子 自旋的組成結構，由 歐洲μ子共同研究 （英语：European Muon Collaboration） （EMC）實施 [1]。 物理學家預計 夸克 會完全負擔質子的 自旋。 然而，夸克所承擔的質子自旋不只是遠遠低於100%而已，實驗結果一致顯示夸克幾乎沒有負擔質子的任何自旋。 這令人驚訝與費解的結果被稱為「質子自旋危機」 [2]。 關鍵問題是核子自旋是如何分 …
How Did the Proton Get Its Spin? | Department of Energy
2017年3月29日 · Protons are one of the three particles that make up atoms, the building blocks of the universe. A proton's spin is one of its most basic properties. Because protons are in part made up of quarks, scientists presumed the proton spins were just the sum of the quark spins. But studies in the 1980s showed that reality is far more complex.
How Does the Proton Spin? | Science - AAAS
In analyzing these collisions, the key questions are: What happens to spin in the transition from current quarks (those probed in high-energy experiments) to constituent quarks (the building blocks of the proton)? How is the spin ½ value of the proton built up from the spins and orbital angular momentum of the quarks and gluons inside?
Theory and experiment combine to shine a new light on proton spin
2024年5月24日 · Now, a new method that combines experimental data with state-of-the-art calculations has revealed a more detailed picture of spin contributions from the very glue that holds protons together....
Proton spin after 30 years: what we know and what we don't?
2020年9月2日 · Much theoretical and experimental progress has been made in understanding the origins of the proton spin. In this review, we will discuss what we have learned so far, what are still missing, and what we shall expect to learn from the upcoming experiments including JLab 12 GeV and Electron-Ion Collider.
Proton puzzles - Nature Reviews Physics
2021年1月8日 · Where does the proton spin come from? The proton is a spin-1/2 particle. It would seem reasonable to assume that its spin comes from the simple arithmetic of three component quarks...