What Are Fermions and Bosons in the Meson Quark Model?

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Discussion Overview

The discussion centers on the definitions and characteristics of fermions and bosons, particularly in the context of the meson quark model. Participants explore the implications of particle spin and the composition of mesons, as well as comparisons between different types of particles such as pions and muons.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants define fermions as particles with half-integer spin (e.g., 1/2, 3/2) and bosons as those with integer spin (e.g., 1, 2, 3), noting the implications for their wave functions.
  • It is proposed that mesons are composed of a quark and an anti-quark, with specific quantum numbers for the six known quarks, which limits the possible combinations for mesons with certain strangeness and charge values.
  • One participant questions the differences between pions and muons, leading to clarifications that pions are mesons while muons belong to the lepton family.
  • Another participant emphasizes that pions are composite particles (mesons) and muons are elementary particles, highlighting a distinction in their nature.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of fermions and bosons, as well as the composition of mesons. However, there is a lack of consensus on the implications of these definitions and the relationships between different particle types, as some distinctions are clarified while others remain open for further discussion.

Contextual Notes

The discussion does not resolve the complexities surrounding the implications of particle spin and the specific combinations of quarks that lead to different meson properties. Some assumptions about the nature of particles and their classifications are also not fully explored.

Flavia
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1) What is mean by fermion with half integer spin and boson with integer spin

Is that fermion, 1/2,3/2...
boson, 1,2,3

2) Why meson don't have q = +1, S = -1 or q = -1, S = +1 in term of quark model
 
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1) Yes, the term "fermion" is referred to particle that have half integer spin (as you said 1/2, 3/2 and so on), while "boson" is referred to particle with integer spin. This have many consequences. First of all the wave function of N fermions must be antisymmetric under exchange of any two of this N fermions, while for bosons it has to be symmetric.

2) In term of quark model a "meson" is a particle composed by a quark and an anti-quark. There are six quarks in nature and their quantum numbers are (considering only charge and strangeness):

UP (u) Q=+2/3 S=0
DOWN (d) Q=-1/3 S=0
CHARM (c) Q=+2/3 S=0
STRANGE (s) Q=-1/3 S=-1
TOP (t) Q=+2/3 S=0
BOTTOM (b) Q=-1/3 S=0

The only way to have a meson with strangeness is to include a strange or anti-strange quark in its composition. So for example, if you want a meson with S=-1 you have to put a strange quark, but for the composition of mesons, the other element must be a anti-quark and as you can see from the list there is no way you can have a total charge Q=+1. The same reasoning is valid for the other combination S=+1 Q=-1.
 
Ok thanks! get it.

What is the differences between pion and muon?
 
A pion is a meson whereas a muon is part of a group of particles called leptons.
 
Also, in our current understanding a pion is a composed particle (is a meson) while the muon is known as an elementary particle.
 

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