Accuracy in determination of masses of quarks,
particulary the lightest ones, still does not exceed of two digits
of accuracy.
For example, for first "family" of quarks data
are following : 1/2(mu+md)=4.2 MeV/c2;
1.5<mu<5 MeV; 5<md<9 MeV/c2
for strange quark ms=0.105ą0.033 GeV/c2
[Manohor 2002]
Most of hadrons mass is originated from quarks energy,
not from their mass. And in that way, quark u mass is just 6 massesof
the electron and simultaneously mp=1837me
Two first measurements of quark t mass :
176ą18 GeV/c2 [Abe et al. 1995]
i 199ą40 GeV/c2 [Abachi et al. 1995]
According
to numerous theories, difference in masses between heavier quarks was very
important during early stages of matter formation, deciding about direction
of exchanges of one type of quarks into others.
u and d quarks have similar mass:
change one d quark into u quark is the reason of radioactive
decay, what is main mechanism keeping high temperature inside the
Earth (during 4,5 billion years).
Quarks are in 3 colors, which are exchanged in strong
interactions (by gluons exchange).
