Quantum Physics: proton makeup confusion (General)

by David Turell , Wednesday, February 24, 2021, 18:05 (1366 days ago) @ David Turell
edited by David Turell, Wednesday, February 24, 2021, 18:22

The proton content of antimatter seems too high:

https://www.sciencenews.org/article/proton-antimatter-lopsided-quark-antiquark

"The proton’s antimatter is out of whack. An imbalance between two types of antiparticles that seethe within the proton is even wonkier than previously thought, a new measurement indicates.

"Protons are built from t­hree quarks — two “up” quarks and one “down” quark. But they also contain a roiling sea of transient quarks and antiquarks that fluctuate into existence before swiftly annihilating one another. Within that sea, down antiquarks outnumber up antiquarks, measurements revealed in the 1990s. And that lopsidedness persists in a realm of quark momenta previously unexplored, researchers report.

"...new tests, made by slamming protons into targets made of hydrogen and deuterium (hydrogen with an extra neutron in its nucleus), contradict that idea. 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.

"The measurements are important for studies at the Large Hadron Collider at CERN in Geneva, which slams protons together to look for new phenomena. To fully understand the collisions, physicists need a thorough accounting of the proton’s constituents. “They need to know what they’re colliding,” says study coauthor Paul Reimer of Argonne National Laboratory in Lemont, Ill."

Comment: Why the human complaint of 'imbalance'? What we find is what God correctly wanted to be present. And we simply need to measure without doubting.

Another take:

https://www.quantamagazine.org/protons-antimatter-revealed-by-decades-old-experiment-20...

In reality, the proton’s interior swirls with a fluctuating number of six kinds of quarks, their oppositely charged antimatter counterparts (antiquarks), and “gluon” particles that bind the others together, morph into them and readily multiply. Somehow, the roiling maelstrom winds up perfectly stable and superficially simple — mimicking, in certain respects, a trio of quarks. “How it all works out, that’s quite frankly something of a miracle,” said Donald Geesaman, a nuclear physicist.

***

The data immediately favors two theoretical models of the proton sea. “This is the first real evidence backing up those models that has come out,” said Reimer.

One is the “pion cloud” model, a popular, decades-old approach that emphasizes the proton’s tendency to emit and reabsorb particles called pions, which belong to a group of particles known as mesons. The other model, the so-called statistical model, treats the proton like a container full of gas.

Planned future experiments will help researchers choose between the two pictures. But whichever model is right, SeaQuest’s hard data about the proton’s inner antimatter will be immediately useful, especially for physicists who smash protons together at nearly light speed in Europe’s Large Hadron Collider. When they know exactly what’s in the colliding objects, they can better piece through the collision debris looking for evidence of new particles or effects.

***

In the ultimate quest to understand the proton, the deciding factor might be its spin, or intrinsic angular momentum. A muon scattering experiment in the late 1980s showed that the spins of the proton’s three valence quarks account for no more than 30% of the proton’s total spin. The “proton spin crisis” is: What contributes the other 70%? Once again, said Brown, the Fermilab old-timer, “something else must be going on.”

***

Alberg and Miller are working on calculations of the full “meson cloud” surrounding protons, which includes, along with pions, rarer “rho mesons.” Pions don’t possess spin, but rho mesons do, so they must contribute to the overall spin of the proton in a way Alberg and Miller hope to determine.

Comment: Note the difference in two authors. The former sounds puzzled. The latter simply describes clarifying research. Moral: know how to interpret what you read in studying scientific reporting. Author bias will show if you are careful.