This has been driven by the observation of many new `exotic~ states that do not fit into the traditional picture of mesons (composed of a quark-antiquark pair) and baryos (three quarks) in the constituent quark model
According to the quark model
, the properties of hadrons are primarily determined by their so-called valence quarks.
Other topics discussed include space-time symmetries, the quark model
of hadrons, quantum chromodynamics and jet physics, the weak interaction (including its unification with the electromagnetic interaction and CP violation and other related symmetries), and some important open questions beyond the standard model that are currently being investigated.
Employing a quark model
with spherically symmetric wave functions, [g.
This was a very curious and unexpected experimental result of the European Muon Collaboration, EMC  (later consolidated by other experiments), as the whole idea of the original quark model
of Gell-Mann  and Zweig  was to account for 100 percent of the hadronic spins, solely in terms of quarks.
The study is a continuation of their 2004 Quark Model
and High Energy Collisions.
In this approach, the authors used a valence quark model
in combination with SU(6) symmetry relations and data on hyperon decays to produce a range of predictions for effective PV meson-nucleon couplings consistent with the SM.
Nonetheless, it is well known that at that time quark model
was not favorite, compared to the geometrical-unification program, in particular for the reason that the quarks have not been observed.
Desplanques, Donoghue, and Holstein (DDH) estimated the nucleon-nucleon-meson weak couplings using quark model
and symmetries arguments and determined a reasonable range of values including their "best guess" values for each of the seven coupling amplitudes .
And in high-energy physics, he adds, the zoo of particles discovered by the 1960s was nicely caged by the elegance of the quark model
That ratio is just right if the star is composed of neutrons, but it's inconsistent with the most plausible quark models
, say Cottam and her collaborators, Frits Paerels of Columbia University and Mariano Mendez of the SRON National Institute for Space Research in Utrecht, the Netherlands.