Sunday school at the Jefferson Lab..
Paul answers a question..
"If different types of quarks have different masses, then why are protons and neutrons said to have the same mass,
when they have different compositions of quarks"
The proton and neutron are each made from three quarks. A proton is made up of two Up quarks and a Down quark
while a neutron is made from two Down quarks and an Up quark
If protons and neutrons only had quarks in them it would be easy algebra to get the quark masses.
However, there is a family of lighter particles called Pions that are made from pairs of quarks.
They are made from pairs of Up and Down quarks. They have masses that are a lot smaller
than two thirds of the proton or neutron mass so determining the masses of the quarks isn't easy!
. We could also set limits on the Up (Down) mass. The Up (Down) quark could be as heavy as the proton mass divided by three. That would make the Up (Down) around 310 MeV on the high end. So where are we with the quark masses by this crude method:
Up ≈ Down ≈ 300 MeV
Strange ≈ 510 MeV
Charmed ≈ 1,500 MeV
Bottom ≈ 4,800 MeV
Top ≈ 91,000 MeV
If we had a theory that could predict the binding energy of the common particles then we could calculate the quark masses. If we could produce free quarks we could simply measure their masses just like we have measured the proton, the electron, the neutron and other particles to very high accuracy. As I said before, free quarks have not been found so we must derive their properties by a mix of theory and experiments. The most successful theory (so far) of the particles is called the Standard Model. It has had great success for the last ~30 years, but it does not predict why the quarks have the apparent masses that they do!
Perhaps one of you will someday work at CERN, Fermilab, or another lab and help make the big discovery!
Paul Brindza, Experimental Hall A Design Leader
It's all baloney. Since it's the wave nature of matter, a more massive particle has a shorter wavelength. Martin van der Mark wrote about this. See on the nature of stuff and the hierarchy of the forces: smaller mass means bigger wavelength, so you can’t fit a longer-wavelength 2.3 MeV quark inside a smaller-wavelength 938.27 MeV proton.
Sadly Martin died on Monday. He had a brain tumour. Very sad. He and his wife Inge stayed overnight at my house a few years back. We had a great evening. His close friend and co-author John Williamson sent an email to large list of people, including me.