Strangeness
A quantum number assigned to particles containing strange quarks. Strangeness is conserved in strong nuclear interactions but violated in weak interactions. Strangeness conservation is one of the selection rules that governs which particles can decay into which others through the weak force.
Formula
S = −1 per strange quark, S = +1 per strange antiquark
Real World
When protons collide at the LHC, kaons (S = ±1) are produced in pairs via the strong force — a positive kaon and negative kaon together keep total strangeness zero, a phenomenon first noticed in cosmic ray cloud chamber photographs in the 1940s.
Exam Focus
Strangeness is conserved in strong interactions but can change by ±1 in weak decays — always state which force is responsible when explaining strangeness change.
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