strangeness quantum number

"Strangeness" in particle physics refers to a quantum number, denoted as S, assigned to certain subatomic particles called "strange" particles. These particles were discovered in cosmic rays and exhibited unusual behavior: they were created in strong interactions but decayed much more slowly than expected, implying they were not governed by the strong force alone.1

To explain this, physicists Murray Gell-Mann and Kazuhiko Nishijima independently proposed that these particles possessed a new property, "strangeness," which is conserved in strong interactions but not in the weaker decay processes. Particles like pions, protons, and neutrons have a strangeness of 0. The strong force can only create strange particles in pairs, ensuring the net strangeness remains zero, a phenomenon known as associated production. This concept was crucial in developing the quark model, where the "strange" quark (s) carries a strangeness quantum number of -1.12