The internal structure of a proton, with quarks, gluons, and quark spin shown. The nuclear force acts like a spring, with negligible force when unstretched but large, attractive forces when stretched ...

For a quarter of a century, physicists have faced a paradox regarding the net spin of protons and neutrons – the spin of their constituent quarks accounts for only a small fraction of their overall ...

"These results confirm our suspicion that a lot of the gluons' contribution to proton spin comes from the gluons with relatively low momentum," said Ralf Seidl, a physicist from the RIKEN-BNL Research ...

One of the great theoretical challenges facing physicists is understanding how the tiniest elementary particles give rise to most of the mass in the visible universe. A physicist from MIT will talk ...

The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. The electrostatic repulsion and the attractive ...

An unusual alliance between physicists who study ultrahot plasmas and ultracold atoms is yielding intriguing results – and may even lead to an experimental test for string theory, as Barbara Jacak ...

The early Universe was a strange place. The Universe was so dense and hot that atoms and nuclei could not form—they would be ripped apart by high-energy collisions. Even protons and neutrons could not ...

Comparing the number of direct photons emitted when proton spins point in opposite directions (top) with the number emitted when protons collide head-to-tail (bottom) revealed that gluon spins align ...

Polarized proton containing spinning quarks and gluons (represented by right-handed and left-handed spirals). The negative Δg solutions (blue) are disfavored relative to the positive Δg solutions (red ...

New data from particle collisions at the Relativistic Heavy Ion Collider (RHIC), an "atom smasher" at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, reveals how the primordial ...

What happens when the smallest building blocks of matter refuse to play by the rules of traditional physics? For decades, atomic nuclei have posed a stubborn puzzle: at low energies, they appear as ...