Prof. S. LAKSHMINARAYANA
Department Of Nuclear Physics, Andhra University, Vizag-530003, AP, India.
Estimated or phenomenological [7, 8] masses of up and down quarks are 1.3 to 3.3 MeV and 4.1 to 5.8 MeV respectively.
Standard model assumes that proton constitutes 2 up quarks and one down quark. Neutron constitutes 2 down quarks and one up quarks.
In any way their estimated or phenomenological [7, 8] mass sum is not matching with the nucleons rest mass.
In any way their sum is not matching with the nucleons rest energy.
There should be some reason for this mismatch. This clearly indicates that there is something missing from the standard model.
In standard model there exists 8 gluons having `color’ charge with no rest mass and in between the quarks strong interaction is mediated by these gluons.
If gluons has no rest mass and up and down quarks mass sum is small (compared to the nucleon rest mass) how to generate the existing nucleon rest mass? To over come this difculty  it is suggested that there exists integral charge quark fermions, integral charge quark bosons, integral charge (massive) quark fermi-gluons and integral charge (massive) quark boso-gluons.
Note that fermi-gluon means massive gluons having fermion behavior and boso-gluon means massive gluons having boson behavior.
(Effective) fermi-gluons play a crucial role in baryons mass generation and boso-gluons play a crucial role in mesons mass generation.