d quark
down quark

For example, the rules above say that a contains a c quark and some combination of two u and/or d quarks.

It is broken by the different masses of the u and d quarks as well as by their different charges.

Since the u and d quarks have similar masses, particles made of the same number then also have similar masses.

Since protons and neutrons are made up of U and D quarks, it's natural that the convenient fiction is continued there.

The success of the isospin model is now understood to be the result of the similar masses of the u and d quarks.

The down quark or d quark (symbol: d) is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter.

Particles of isospin 1 are made of a mix of two u and d quarks (Pi mesons, Rho mesons, Sigma baryons with one heavier quark, etc.).

Particles of isospin 0 can be made of one u and one d quark (Eta mesons, Omega mesons, Lambda baryons, etc.), or from no u or d quarks at all (Omega baryons, Phi mesons, etc.), with heavier quarks in all cases.

That is for the up and down quarks in the nucleus.

Only up and down quarks are found inside atoms of the normal matter.

A neutron is made of two down quarks and one up quark.

An up quark and a down quark are not the same thing.

Two of these are up quarks, one of them is a down quark.

Neutrons, with no charge, have one up quark and two down quarks.

The mass of up and down quarks are much less the mass than electrons.

These transformations have no effect at all on an electron, because it contains neither up nor down quarks.

They are baryons containing no up or down quarks.

All the ordinary atomic nuclei in the universe are constructed from up and down quarks.

Protons and neutrons are made of up and down quarks.

Bottom quarks have a charge of -1/3, similar to down quarks.

Up and down quarks have the lowest masses of all quarks.

Down quarks are most commonly found in nucleons.

Each proton is, in turn, composed of 3 elementary particles: two up quarks and one down quark.

In a proton, whose charge is +1, there are two up quarks and one down quark.

For example, would turn all up quarks in the universe into down quarks and vice-versa.

Each neutron is made of two downs quarks and an up, which means the net charge is zip.

Down quarks are the second lightest quark, the first being up quarks.

Quarks are able to change from up quarks to down quarks.

Positron emission happens when an up quark changes into a down quark.

This includes the up and down quarks, and to a lesser extent the strange quark, but not any of the others.

Particles made of the same numbers of up and down quarks have similar masses and are grouped together.

Bottom quarks are a heavier counterpart to the down quarks that make up most of the matter we normally experience.

This element relates very accurately the likelihood that top quarks decay to down quarks.