Azurite said:
May I know how much LHC has constraint the parameter space of the subquarks (generally known as preons)?
What models are still viable (I'm focusing on the subquarks and not other particles like electrons as made of smaller components)?
I hope ohwilleke can share some insight as he is the lead author of preons in the Wikipedia. And others knowledable about subquarks side of preons.
I'm studying strong force confinement and I wonder if the quarks are sufficient or we really need subquarks to make it work. What is your opinion?
Here are two specific questions to narrow them down:
1. The quark discovery used small electron probe in the SLAC accelerator.. this required because you needed smaller probe or bullet to reveal the scattering centers.. see
https://www.learner.org/courses/physics/unit/text.html?unit=1&secNum=5
"By the early 1970s, detailed analyses of the distribution of the scattered electrons measured in the giant magnetic spectrometers in End Station A revealed three scattering centers within the nucleon—the first experimental evidence that quarks were in fact real. Physicists Jerome Friedman, Henry Kendall, and Richard Taylor received the Nobel Prize for this discovery in 1990."
The LHC collides hadrons so how can it have the resolution to see quarks in a nucleon and much less subquarks??
2. About the mass paradox
https://en.wikipedia.org/wiki/Preon
"The mass paradox
One preon model started as an internal paper at the Collider Detector at
Fermilab (CDF) around 1994. The paper was written after an unexpected and inexplicable excess of jets with energies above 200
GeV were detected in the 1992–1993 running period. However,
scattering experiments have shown that quarks and leptons are "pointlike" down to distance scales of less than 10−18 m (or 1/1000 of a proton diameter). The
momentum uncertainty of a preon (of whatever mass) confined to a box of this size is about 200 GeV/c, 50,000 times larger than the
rest mass of an up-quark and 400,000 times larger than the rest mass of an electron.
Heisenberg's
uncertainty principle states that ΔxΔp ≥ ħ/2 and thus anything confined to a box smaller than Δx would have a momentum uncertainty proportionally greater. Thus, the preon model proposed particles smaller than the elementary particles they make up, since the momentum uncertainty Δp should be greater than the particles themselves. And so the preon model represents a mass paradox: How could quarks or electrons be made of smaller particles that would have many orders of magnitude greater mass-energies arising from their enormous momenta? This paradox is resolved by postulating a large binding force between preons cancelling their mass-energies.[
citation needed]"
Is this like a fine tuning thing like the cosmological constant problem or the higgs hierarchy problem or the fine tuning more manageable and possible? What other existing particles have this cancellation analogy in other properties or aspects of the parameter space?