Delta baryon

Properties

Four closely related Δ baryons exist: Δ⁺⁺
(constituent quarks: uuu), Δ⁺
(uud), Δ⁰
(udd), and Δ⁻
(ddd), which respectively carry an electric charge of +2 e, +1 e, 0 e, and −1 e.

The Δ baryons have a mass of about 1232 MeV/c²; their third component of isospin ${\displaystyle I_3=\pm \frac{1}{2}\mathsf{o}\mathsf{r}\pm \frac{3}{2};}$ and they are required to have an intrinsic spin of ⁠ 3 /2⁠ or higher (half-integer units). Ordinary nucleons (symbol N, meaning either a proton or neutron), by contrast, have a mass of about 939 MeV/c², and both intrinsic spin and isospin of ⁠1/ 2 ⁠. The Δ⁺
(uud) and Δ⁰
(udd) particles are higher-mass spin-excitations of the proton (N⁺
, uud) and neutron (N⁰
, udd), respectively. The Δ⁺⁺
and Δ⁻
, however, have no direct nucleon analogues: For example, even though their charges are identical and their masses are similar, the Δ⁻
(ddd), is not closely related to the antiproton (p, uud).

The Delta states discussed here are only the lowest-mass quantum excitations of the proton and neutron. At higher spins, additional higher mass Delta states appear, all defined by having constant ⁠ 3 /2⁠ or ⁠ 1 /2⁠ isospin (depending on charge), but with spin ⁠ 3 /2⁠, ⁠ 5 /2⁠, ⁠ 7 /2⁠, ..., ⁠ 11 /2⁠ multiplied by ħ. A complete listing of all properties of all these states can be found in Beringer et al. (2013).

There also exist antiparticle Delta states with opposite charges, made up of the corresponding antiquarks.