Current quarks are defined as the constituent quark

Constituent quark

A constituent quark is a current quark with a covering.In the low energy limit of QCD, a description by means of perturbation theory is not possible. Here, no Asymptotic freedom exists, but the interactions between valence quarks and sea quarks gain strongly on significance...

 cores (constituent quarks with no covering) of a valence quark.

If, in one constituent quark, the current quark is hit inside the covering with large force, it accelerates through the covering and leaves it behind. In addition, current quarks possess one asymptotic freedom

Asymptotic freedom

In physics, asymptotic freedom is a property of some gauge theories that causes interactions between particles to become arbitrarily weak at energy scales that become arbitrarily large, or, equivalently, at length scales that become arbitrarily small .Asymptotic freedom is a feature of quantum...

 within the perturbation theory

Perturbation theory

Perturbation theory comprises mathematical methods that are used to find an approximate solution to a problem which cannot be solved exactly, by starting from the exact solution of a related problem...

 described limits. In quantum chromodynamics

Quantum chromodynamics

In theoretical physics, quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...

, the mass of the current quarks carries the designation current quark mass

Current quark mass

The current quark mass is also called the mass of the 'naked' quarks.The mass of the current quark is reduced by the term of the constituent quark covering mass.The current quark mass is a logical consequence of the mathematical formalism of the QFT,...

.

The local term plays no more role for the description of the hadrons with the light current quarks:

Current quark	Mass	Δx
Up quark Up quark The up quark or u quark is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons and protons of atomic nuclei...	5–	20–
Down quark Down quark The down quark or d quark is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the up quark, forms the neutrons and protons of atomic nuclei...	5–	20–
Strange quark Strange quark The strange quark or s quark is the third-lightest of all quarks, a type of elementary particle. Strange quarks are found in hadrons, which are subatomic particles. Example of hadrons containing strange quarks include kaons , strange D mesons , Sigma baryons , and other strange particles...
Charm quark Charm quark The charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
Bottom quark Bottom quark The bottom quark, also known as the beauty quark, is a third-generation quark with a charge of − e. Although all quarks are described in a similar way by the quantum chromodynamics, the bottom quark's large bare mass , combined with low values of the CKM matrix elements Vub and Vcb, gives it a...
Top quark Top quark The top quark, also known as the t quark or truth quark, is an elementary particle and a fundamental constituent of matter. Like all quarks, the top quark is an elementary fermion with spin-, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and...

A description is only possible with the help of relativistic quantum mechanics.