The delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols Δ++, Δ+, Δ0, and Δ− and electric charges +2, +1, 0 and −1 elementary charge respectively. Like nucleons, they are relatively light (1,232 MeV/c2) baryons made of only up (u) and down (d) quarks, but unlike nucleons, they have both spin and total isospin equal to 3⁄2.
The four different particles that make up the delta family are distinguished by their electrical charges, which is the sum of the charges of the mixture of up (u) and down (d) quarks of which they are composed. There are also four antiparticles with opposite charges, made up of the corresponding antiquarks. The existence of the Δ++, with its unusual +2 charge, was a crucial clue in the development of the quark model.
The 3⁄2 spin means that all the three quarks inside a Δ particle have their spin axis pointing in the same direction, unlike the nearly identical proton and neutron in which the intrinsic spin of one of the three constituent quarks is always opposite the spin of the other two. This spin alignment is complemented by a total isospin quantum number of 3⁄2 which differentiates[how?] the Δ+ and Δ0 and ordinary nucleons, which have spin and isospin of 1⁄2.
All varieties of Δ quickly decay via the strong force into a nucleon (proton or neutron) and a pion of appropriate charge. The amplitudes of various final charge states given by their respective isospin couplings. More rarely and more slowly, the Δ+ can decay into a proton and a photon and the Δ0 can decay into a neutron and a photon.
|Rest mass (MeV/c2)||I3||JP||Q (e)||S||C||B′||T||Mean lifetime (s)||Commonly decays to|
|Delta||Δ++(1232)||uuu||1,232 ± 1||+3⁄2||3⁄2+||+2||0||0||0||0||5.58±0.09×10−24[a]||p+ + π+|
|Delta||Δ+(1232)||uud||1,232 ± 1||+1⁄2||3⁄2+||+1||0||0||0||0||5.58±0.09×10−24[a]||π+ + n0 or
|Delta||Δ0(1232)||udd||1,232 ± 1||−1⁄2||3⁄2+||0||0||0||0||0||5.58±0.09×10−24[a]||π0 + n0 or
|Delta||Δ−(1232)||ddd||1,232 ± 1||−3⁄2||3⁄2+||−1||0||0||0||0||5.58±0.09×10−24[a]||π− + n0|
- C. Amsler et al. (2008): Particle listings – Δ(1232)
- C. Amsler et al. (Particle Data Group) (2008). "Review of Particle Physics". Physics Letters B 667 (1): 1. Bibcode:2008PhLB..667....1P. doi:10.1016/j.physletb.2008.07.018.