Collisions of polarized protons (beam entering from left) and unpolarized protons (right) result in the production of W bosons (in this case, W-). RHIC's detectors identify the particles emitted as the W bosons decay (in this case, electrons, e-) and the angles at which they emerge. The colored arrows represent different possible directions, which probe how different quark flavors -- e.g., an "up" antiquark (u) and a "down" quark (d) -- contribute to the proton spin. (Credit: STAR Collaboration.)

Sea Quark Surprise Reveals Deeper Complexity in Proton Spin Puzzle

Story in collaboration with Brookhaven National Laboratory

Feb 25, 2019