Being baryons, all hyperons are fermions. That is, they have half-integer spin and obey Fermi-Dirac statistics. They all interact via the strong nuclear force, making them types of hadron. They are composed of three light quarks, at least one of which is a strange quark, which makes them strange baryons. Hyperons decay weakly with non-conserved parity.
There are three Sigma hyperons, , and . They have rest energies of ~ and lifetimes of ~ with the exception of whose lifetime is shorter than .
There is one Lambda hyperon, . It has a rest energy of with a lifetime of .
There are two Xi hyperons, and . They have rest energies of and and lifetimes of and .
There is one Omega hyperon, the last discovered, , with a mass of and a lifetime of .
The has a baryon number of +1 and hypercharge of -2 giving it strangeness of −3. It takes multiple flavor-changing weak decays for it to decay into a proton or neutron. Murray Gell-Mann's SU(3) model (sometimes called the Eightfold Way) predicted this hyperon's existence, mass and that it will only undergo weak decay processes.
Experimental evidence for its existence was discovered in 1964 at Brookhaven National Laboratory. Further examples of its formation and observation using particle accelerators confirmed the SU(3) model. → + → + → +
|Particle||Symbol||Makeup|| Rest mass|
|Q||S||C||B|| Mean lifetime|
|Commonly decays to|
|Lambda||1 115.683(6)||0||+||0||−1||0||0|| |
|Sigma||1 189.37(0.7)||1||+||+1||−1||0||0|| |
|Sigma resonance||(1385)||1 382.8(4)||1||+||+1||−1||0||0||or|
|Sigma resonance||(1385)||1 383.7±1.0||1||+||0||−1||0||0||or|
|Sigma resonance||(1385)||1 387.2(5)||1||+||−1||−1||0||0||or|
|Xi resonance||(1530)||1 531.80(32)||+||0||−2||0||0|
|Xi resonance||(1530)||1 535.0(6)||+||−1||−2||0||0|
|Omega||1 672.45(29)||0||+||−1||−3||0||0|| or |
Science past: from the issue of March 24, 1962.(SCIENCE NOTEBOOK)(discovery of anti-Xi-minus antiparticles)(Brief article)
Mar 24, 2012; ANTI-PARTICLE DISCOVERED--Three international teams of scientists, working in the United States, Switzerland and France, have...