Scientists face challenges in directly measuring the mass of quarks within atoms due to a phenomenon called confinement. Confinement refers to the fact that quarks are always bound together within particles and cannot be observed as free particles in isolation.
Quarks are elementary particles that are fundamental constituents of matter. They combine to form composite particles known as hadrons, which include protons and neutrons. Quarks are held together by the strong nuclear force, mediated by particles called gluons.
The strong force is characterized by its property of increasing in strength as quarks are pulled apart. As the separation between quarks increases, the energy stored in the field between them also increases. This phenomenon leads to the formation of additional quark-antiquark pairs, resulting in the creation of new hadrons.
Due to confinement, quarks are always observed in bound states and cannot be directly isolated or detected as individual particles. When scientists attempt to separate quarks, the energy required to do so is used to create new quark-antiquark pairs, forming new bound states instead of revealing the individual quark masses.
However, while direct measurements of quark masses within hadrons are challenging, scientists use various theoretical and experimental techniques, such as lattice QCD (Quantum Chromodynamics), to determine the masses of quarks indirectly. These methods involve calculations based on fundamental principles and constraints provided by experimental data, leading to estimates of quark masses within the context of the Standard Model of particle physics.