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In particle physics, strangeness (symbol S) [1] [2] is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic interactions that occur in a short period of time. The strangeness of a particle is defined as: = (¯) where n s
A strange particle is an elementary particle with a strangeness quantum number different from zero. Strange particles are members of a large family of elementary particles carrying the quantum number of strangeness, including several cases where the quantum number is hidden in a strange/anti-strange pair, for example in the ϕ meson.
)) to explain the "strangeness" of the longer-lived particles. The Gell-Mann–Nishijima formula is the result of these efforts to understand strange decays. Despite their work, the relationships between each particle and the physical basis behind the strangeness property remained unclear.
The discovery of hadrons with the internal quantum number "strangeness" marks the beginning of a most exciting epoch in particle physics that even now, fifty years later, has not yet found its conclusion ... by and large experiments have driven the development, and that major discoveries came unexpectedly or even against expectations expressed ...
The terms "strange" and "strangeness" predate the discovery of the quark, but continued to be used after its discovery for the sake of continuity (i.e. the strangeness of each type of hadron remained the same); strangeness of anti-particles being referred to as +1, and particles as −1 as per the original definition.
In particle physics and astrophysics, the term 'strange matter' is used in two different contexts, one broader and the other more specific and hypothetical: [1] [2]. In the broader context, our current understanding of the laws of nature predicts that strange matter could be created when nuclear matter (made of protons and neutrons) is compressed beyond a critical density.
The discovery was announced on 12 June 2007. It was the first known particle made of quarks from all three quark generations – namely, a down quark, a strange quark, and a bottom quark. The DØ and CDF collaborations reported the consistent masses of the new state. The Particle Data Group world average mass is 5.7924 ± 0.0030 GeV/c 2.
have zero total isospin, I, and zero strangeness, and hypercharge. Each quark which appears in an η particle is accompanied by its antiquark, hence all the main quantum numbers are zero, and the particle overall is "flavourless".