11. Baryons, Mesons and Particle Accelerators Flashcards
What spin do quarks have?
1/2
How many quarks do baryons have?
3
What spin does a quark pair have?
0 or 1
What is the spin of a baryon?
1/2 or 3/2
Give two examples of baryons with spin 1/2
- Proton
- Neutron
What are the allowed spin-3/2 baryons?
S = strangeness
What are the allowed spin-1/2 baryons?
S = strangeness
Why aren’t ddd, uuu, sss spin-1/2 baryons observed in nature?
The Pauli Exclusion Principle forbids more than one fermion from occupying the same quantum state.
What is the ket notation for a symmetric 2-particle wavefunction?
What is the ket notation for an antisymmetric 2-particle wavefunction?
Give the equation for the overall wavefunction of baryons
ψ = wavefunction
The 4 terms of the baryon wavefunction equation are _________.
Seperable
How can an antisymmetric total wavefunction of baryons be found based on the overall wavefunction equation?
By multiplying 3 symmetric wavefunctions by an anti-symmetric wavefunction.
Are spin wave functions symmetric or anti-symmetric on particle exchange?
Symmetric
Are spatial wave functions symmetric or anti-symmetric on particle exchange?
Symmetric
Are flavour wave functions symmetric or anti-symmetric on particle exchange?
Symmetric
Are colour wave functions symmetric or anti-symmetric on particle exchange?
Anti-symmetric
Give the equation for the flavour wavefunction of a baryon
Give the equation for the colour wavefunction of a baryon
Why is the colour wavefunction for baryons known as the colour singlet?
Because there is only one possible state. All known baryons have colour wavefunctions of this form.
State the normalised spin wavefunction for the singlet (s = 0) state
Is the singlet state wavefunction symmetric or anti-symmetric?
Anti-symmetric
State the normalised spin wavefunction for a triplet (s = 1) state
Is the triplet state wavefunction symmetric or anti-symmetric?
Symmetric
How are quarks combined to form spin-3/2 baryons with a symmetric spin wavefunction?
A quark is added to the 2 quark s = 1 triplet state, making it symmetric.
State the 4 spin wavefunctions of spin-3/2 baryons
Why are there spin-3/2 baryons with the same quark structure as protons and neutrons?
They are higher energy excited states of protons and neutrons.
How are quarks combined to form spin-1/2 baryons?
Either by adding a third quark to the 2-quark s = 1 triplet state or to the 2-quark s = 0 singlet state
State the 2 spin wavefunctions of spin-1/2 baryon from a s = 0 starting state
State the 2 spin wavefunctions of spin-1/2 baryon from a s = 1 starting state
What type of symmetry to spin-1/2 baryons have?
Partial symmetry (symmetrical on 2 out of 3 of the quarks)