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Parity Violation: The Biggest Scientific Blunder of the 20th Century?

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### 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
- Round Earth
- Heliocentric view of Universe
- Special Relativity (time is not absolute)
- General relativity (spacetime is curved)
- Big bang – Universe finite in space and time
- Expanding Universe (time asymmetry)

Plan

- Parity violation – the conventional view
- My interest
- Review of Parity conservation
- Mechanics
- Electromagnetism
- Weak Interactions
- An alternative view
- Parity is Conserved !!

Before

After

Effect of Parity - momentumThe Parity Operator gives the transformation due an inversion of the spatial coordinates

Physical Review October 1956 p254-258

Parity violation in the weak interactions

Tsung Dao Lee

Chen Ning Yang

Look for an asymmetric outcome

Start with a symmetrical statee-

θ

60Ni + e- +υe

60Co

I(θ)dθ = k (1 + αcosθ )sinθdθ

I(θ)dθ = k (1 –v/c cosθ )sinθdθ

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:

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

Doh !!

Where have they gone wrong?

- Exactly what has been observed?
- Exactly what has been violated?
- What, exactly, is the definition of Parity?

Parity in Newtonian Mechanics

Parity conserved

Before

After

F = ma

E = ½m v2

F = m(-a)

-F = m (-a)

-F = (-m)(-a)

F = (-m)(-a)

(± )E = ½(± m) v2

Parity in Newtonian Mechanics

P operator is chosen:

- For simplicity
- To conserve parity
- Supported by:

Special Relativity: (t-component of the energy momentum 4-vector)

General Relativity:

Parity in Electromagnetism

Parity conserved

Before

After

F = q(E + v x B)

Note:

-F = q(-E + -v x (-B))

-F = q(-E + -v x B)

-F = -q(E + -v x B)

-F = -q(E + -v x (-B))

Duality Transforamtion

- The roles of E and B can be reversed by a duality transformation:

Parity in Electromagnetism

P operator is chosen:

- To conserve parity
- For simplicity
- Supported by the covariant formulation:

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?

“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 !

Conclusions

- Space Inversion is a symmetry of Nature
- Parity is conserved
- The conventional P operator is not conserved.

Just a change of convention?

- The conventional P operator may be combined with another transformation of degenerate multiplets. (eg particle anti-particle, neutrino flavours)
- Impacts on unifying theories.

“Not merely a matter of convention: on other particles P could have the usual effect.”

Weinberg

Parity violation

How could they get it so wrong?

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!

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.

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