Strangeness

In <a href="/facts/Particle_physics/YgIuyj2t">particle physics</a>, strangeness (symbol S) is a <a href="/facts/Physical_property/ujcMUceW">property</a> of <a href="/facts/Particle/JHKr2w6h">particles</a>, expressed as a <a href="/facts/Quantum_number/AByP6F0y">quantum number</a>, for describing <a href="/facts/Particle_decay/3koAz34P">decay</a> of particles in <a href="/facts/Strong_interaction/JjRsKcLg">strong</a> and <a href="/facts/Electromagnetic_interaction/oAkmALHT">electromagnetic interactions</a> that occur in a short period of <a href="/facts/Time/HceJKUGB">time</a>. The strangeness of a particle is defined as:

S
        =
        −
        (
        
          n
          
            s
          
        
        −
        
          n
          
            
              
                s
                ¯
              
            
          
        
        )
      
    
    {\displaystyle S=-(n_{\text{s}}-n_{\bar {\text{s}}})}

where ns represents the number of <a href="/facts/Strange_quark/VDWd3ky0">strange quarks</a> (s) and ns represents the number of <a href="/facts/Strange_antiquark/VDWd3ky0">strange antiquarks</a> (s). Evaluation of <a href="/facts/Strangeness_production/URq6mIS4">strangeness production</a> has become an important tool in search, discovery, observation and interpretation of <a href="/facts/Quark%E2%80%93gluon_plasma/TQ8RPydR">quark–gluon plasma</a> (QGP). Strangeness is an excited state of matter and its decay is governed by <a href="/facts/Cabibbo%E2%80%93Kobayashi%E2%80%93Maskawa_matrix/7ckdsIcX">CKM mixing</a>. 
The terms strange and strangeness predate the discovery of the quark, and were adopted after its discovery in order to preserve the continuity of the phrase: strangeness of particles as −1 and anti-particles as +1, per the original definition. For all the quark flavour quantum numbers (strangeness, <a href="/facts/Charm_(quantum_number)/zDxKQ5We">charm</a>, <a href="/facts/Topness/9zpMthh9">topness</a> and <a href="/facts/Bottomness/U3K35l9j">bottomness</a>) the convention is that the flavour charge and the electric charge of a quark have the same sign. With this, any flavour carried by a charged <a href="/facts/Meson/9R0kIc1q">meson</a> has the same sign as its charge.

Strangeness open-in-new

Strangeness