antiquark

Yet Miller calls this rival model “descriptive, rather than predictive,” since it’s tuned to fit data rather than to identify a physical mechanism behind the down antiquark excess.

Models made different predictions for how the ratio of down and up antiquarks should change as you count antiquarks that carry more energy.

When the “NuSea” experiment at Fermilab measured the down-to-up ratio as a function of antiquark momentum in 1999, their answer “just lit everybody up,” Alberg recalled.

Then, a decade later, another group saw hints of puzzling variations in the down-to-up antiquark ratio.

SeaQuest researchers found that down antiquarks were about 50 percent more prevalent than up antiquarks — even when a single antiquark carried nearly half the proton’s total momentum.