Parity Violation:
The Biggest Scientific Blunder
of the 20th Century?
Dr Mark Hadley
Is Nature Symmetrical?
We thought so until 1956 !!
A Major change in our view of space and time
1. Round Earth
2. Heliocentric view of Universe
3. Special Relativity (time is not absolute)
4. General relativity (spacetime is curved)
5. Big bang – Universe finite in space and time
6. Expanding Universe (time asymmetry)
Mark Hadley
Plan
• Parity violation – the conventional view
• My interest
• Review of Parity conservation
– Mechanics
– Electromagnetism
– Weak Interactions
• An alternative view
– Parity is Conserved !!
Mark Hadley
Space Inversion
Inversion = reflection + 180° rotation
 x   x 
   
y

y
P :    
 z   z 
   
t  t 
x  -x
t t
v = x  -v
a = x  -a
ω = r×v  ω
Axial or Pseudo vector
Mark Hadley
Effect of Parity - momentum
The Parity Operator gives the transformation due an
inversion of the spatial coordinates
Before
After
Mark Hadley
Effect of Parity - spin
Before
After
Mark Hadley
Parity violation in the weak
interactions
Tsung Dao Lee
Chen Ning Yang
Physical Review October 1956 p254-258
Mark Hadley
Start with a
symmetrical
state
Look for an
asymmetric
outcome
e-
60Co
θ
60Ni
+ e- +υe
I(θ)dθ = k (1 + αcosθ )sinθdθ
Experimentalists
Wu
Ambler
Hayward
Hoppes
Hudson
National Bureau of Standards USA 1956
Mark Hadley
actual result
I(θ)dθ = k (1 –v/c cosθ )sinθdθ
Parity violation in the weak
interactions
Tsung Dao Lee
Chen Ning Yang
Nobel prize winners 1957
Mark Hadley
But not quite so simple…….
Is the initial state symmetrical?
“We see from this analysis that the logical path from the observed
asymmetry to the inferred nonconservation of parity in β decay
is considerably more complex than the popular presentations
would indicate.”
L. E. Ballentine:
Mark Hadley
A gravitational explanation for
quantum theory
• Aims to explain
– QM
– Particle spectrum
– Fundamental interactions
• Predictions
– No graviton (Gravity waves are just classical waves)
– Spin-half
–Parity is conserved
Mark Hadley
Parity is violated - FACT
All the books say so.
The Nobel Prize
Committee say so.
Mark Hadley
Doh !
Explanations using GR


• Boundary Conditions
• Common source
Mark Hadley
Doh
!!
Doh!!
Where have they gone wrong?
• Exactly what has been observed?
• Exactly what has been violated?
• What, exactly, is the definition of Parity?
Mark Hadley
Parity in Newtonian Mechanics
Before
F = ma
After
Parity
conserved




F = m(-a)
-F = m (-a)
-F = (-m)(-a)
F = (-m)(-a)
E = ½m v2
(± )E = ½(± m) v2
Mark Hadley
Parity in Newtonian Mechanics
P operator is chosen:
1) For simplicity
2) To conserve parity
3) Supported by: E  mc2
Special Relativity: (t-component of the energy
momentum 4-vector)
General Relativity:
1
m
16c 2
 
k
g jk   j g kk dS j
Mark Hadley
Parity in
electromagnetism
e-
Start with a
symmetrical
state……
e-
e-
ee-
e-
Magnetic field pointing out
Parity in Electromagnetism
Before
Parity
conserved
After
F = q(E + v x B)
-F = q(-E + -v x B)
Note:
q
 E.nˆ dS




-F = q(-E + -v x (-B))
-F = -q(E + -v x B)
-F = -q(E + -v x (-B))
Mark Hadley
Parity on magnetic poles
Qm   B.nˆ dS
 Qm   B.(nˆ )dS
Parity in
electromagnetism
e-
e-
ee-
e-
Magnetic field pointing out
e-
eee-
e-
Magnetic field pointing in
Duality Transforamtion
• The roles of E and B can be
reversed by a duality
transformation:
E'  E cos   B sin 
B'  E sin   B cos 
Mark Hadley
Parity in Electromagnetism
P operator is chosen:
1) To conserve parity
2) For simplicity
In this order
3) Supported by the
covariant formulation:
 0

 Ex

F
 Ey

  Ez
Ex
Ey
0
Bz
 By
 Bz
0
Bx
Ez 

By 
 Bx 

0 
4
dF 
J
c
d*F  0
Effect of Parity
The Parity Operator gives the transformation due an
inversion of the spatial coordinates.
We do not have a free choice of P operator.
What are the transformations in beta decay?
Mark Hadley
“We see from this analysis that the logical path from the observed
asymmetry to the inferred nonconservation of parity in β decay
is considerably more complex than the popular presentations
would indicate.”
L. E. Ballentine:
The assumption that the Cobalt nucleous is
symmetrical is not only non-trivial it may well be wrong !
Mark Hadley
What is the mirror image of a
Cobalt atom?
e+
60Co
60Co
e-
Anti 60Co
(not to scale)
e-
Parity
• Reverses
– Momentum
– Lepton number etc.
– Charge
• Unchanged
– Spin
Is conserved
Mark Hadley
Conclusions
• Space Inversion is a symmetry of
Nature
• Parity is conserved
• The conventional P operator is not
conserved.
Mark Hadley
Just a change of convention?
• The conventional P operator may be
combined with another transformation of
degenerate multiplets. (eg particle antiparticle, neutrino flavours)
• Impacts on unifying theories.
“Not merely a matter of convention: on other
particles P could have the usual effect.”
Weinberg
Mark Hadley
Parity violation
How could they get it so wrong?
Mark Hadley
How could they get it so wrong?
• The Parity operation was defined before the
experiments were done.
– Particles were defined as eigenstates of Parity.
– Simplicity of the operator took precendence over
conservation - even though QFT required particles
and antiparticles to be combined in the same
equations.
• There was no higher theory to appeal to.
Watch this space!
Mark Hadley
Parity is
Conserved
Mark Hadley
Eigenvectors of P,
H,J3 with eigenvalues
0,M,σ
Parity
 k ,
 k ,
 p ,
  p ,
Lorentz
Boost
Mark Hadley
CP violation
• Boundary conditions
– Matter dominated Universe
• T asymmetry (CPT theorem)
– Expanding Universe
• Parity = CP for some particles only!
• More complicated effects of P on other
degeneracies.
Mark Hadley