How are quark masses determined experimentally?

[Bobhawke]

Question in title. Indeed, how are any particle masses determined? And especially quarks, since they have the added difficulty of being confined.

 

[genneth]

In general, a particle mass is determined by observing resonance peaks in scattering. Breit-Wigner sounds familiar? The width of the peak gives the lifetime.

Quarks are another matter, as you've noted. In the quark model of hadrons, it is assumed that binding energies follow simple forms, and quarks make up the rest of the mass. A simple data fit is then used. A lot of hadrons fit into this pattern, but several do not.

In QCD, the bare quark masses are very small. Very, very, small. All of the mass of hadrons are considered to due to localisation energy or imperfect cancellation of colour charge.

In deep scattering experiments, the masses are determined running the renormalisation group for a bit and will interpolate between the bare mass and the fitted mass of the quark model for hadrons.

 

[sir-pinski]

The masses of particles, including quarks, are determined experimentally through a variety of methods in particle physics. One common method is through the use of particle accelerators, which allow scientists to collide particles at high energies and study the resulting interactions.

In the case of quarks, their masses cannot be measured directly because they are always confined within particles such as protons and neutrons. However, through the study of the interactions of these particles, scientists can infer the masses of the quarks within them.

One way to do this is through the use of scattering experiments, where particles are bombarded with high-energy beams and the resulting scattered particles are measured. By comparing the expected results based on theoretical models with the actual measured data, scientists can determine the masses of the quarks within the particles being studied.

Another method is through the study of the decays of particles containing quarks. By measuring the energies and momenta of the particles produced in these decays, scientists can again infer the masses of the quarks involved.

Additionally, the masses of quarks can also be determined through precision measurements of other physical quantities, such as the mass of the proton or the energy levels of certain atoms. These measurements are highly sensitive to the underlying masses of the constituent quarks and can provide valuable information about their values.

Overall, determining the masses of quarks and other particles is a complex and ongoing process in particle physics, involving a combination of theoretical models and experimental data. Through continued research and advancements in technology, we are constantly improving our understanding of the fundamental particles that make up our universe.