- 249 Views
- Uploaded on
- Presentation posted in: General

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

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

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

Dr Mark Hadley

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)

- Parity violation – the conventional view
- My interest
- Review of Parity conservation
- Mechanics
- Electromagnetism
- Weak Interactions

- An alternative view
- Parity is Conserved !!

Inversion = reflection + 180° rotation

Axial or Pseudo vector

Before

After

The Parity Operator gives the transformation due an inversion of the spatial coordinates

Before

After

Parity violation in the weak interactions

Tsung Dao Lee

Chen Ning Yang

Look for an asymmetric outcome

e-

θ

60Ni + e- +υe

60Co

I(θ)dθ = k (1 + αcosθ )sinθdθ

Wu Ambler Hayward Hoppes Hudson

National Bureau of Standards USA 1956

actual result

I(θ)dθ = k (1 –v/c cosθ )sinθdθ

Parity violation in the weak interactions

Tsung Dao Lee

Chen Ning Yang

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:

- Aims to explain
- QM
- Particle spectrum
- Fundamental interactions

- Predictions
- No graviton (Gravity waves are just classical waves)
- Spin-half
- Parity is conserved

The Nobel Prize Committee say so.

All the books say so.

Doh !

- Boundary Conditions
- Common source

Doh!!

Doh !!

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

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

P operator is chosen:

- For simplicity
- To conserve parity
- Supported by:
Special Relativity: (t-component of the energy momentum 4-vector)

General Relativity:

e-

e-

e-

e-

e-

Parity in electromagnetism

Start with a symmetrical state……

e-

Magnetic field pointing out

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))

e-

e-

e-

e-

Parity in electromagnetism

e-

Magnetic field pointing out

e-

e-

e-

e-

e-

Magnetic field pointing in

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

In this order

P operator is chosen:

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

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 !

e-

e+

Anti 60Co

60Co

60Co

e-

(not to scale)

- Reverses
- Momentum
- Lepton number etc.
- Charge

- Unchanged
- Spin

- Is conserved

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

- 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

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!

Eigenvectors of P, H,J3 with eigenvalues 0,M,σ

Parity

Lorentz Boost

- 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.