|Mass:||4 - 8 MeV/c2|
|Electric charge:||-1/3 e|
The down quark is a first-generation quark with a charge of -(1/3)e. It is the second-lightest of all quarks. Its bare mass is not well determined, but probably lies between 4 and 8 MeV. According to the Standard Model of particle physics, it and the up quark are the fundamental constituents of the nucleons; the proton contains one down quark and two up quarks, while the neutron contains two down quarks and one up quark. Note, however, that the majority of the mass in nucleons comes from the energy in the gluon field holding the quarks together, and not the quark masses themselves.
Hadrons containing down quarks
Some of the hadrons containing down quarks include:
- Charged Pions (Template:SubatomicParticle) are mesons containing an up quark and an anti-down quark, or vice versa.
- The neutral pion (Template:SubatomicParticle) is a linear combination of up-antiup and down-antidown, as are the Template:SubatomicParticle and ω mesons.
- The Template:SubatomicParticle and Template:SubatomicParticle flavorless mesons are linear combinations of several quark-antiquark pairs, including down-antidown.
- A large number of detected baryons contain one or more down quarks. Like the nucleons, the Template:SubatomicParticle baryons are made of only up and down quarks: the Template:SubatomicParticle contains no down quark, but the Template:SubatomicParticle contains one, the Template:SubatomicParticle contains two, and the Template:SubatomicParticle contains three.