# Presentation: 090507

## The Polarized-Electron Deuteron Experiment and Its Impact on High Energy Physics

- On the Occasion of the CharlieFest
- January 27, 2006
*Robert Cahn*
*LBNL*

## Speaker’s Credentials

- R. Cahn - CharlieFest

- January 27, 2006

## SLAC Giants            

- “There were giants in the earth in those days;
- ...the same became mighty men which were of old, men of renown." *Genesis 6:4*.

- R. Cahn - CharlieFest

- January 27, 2006

## Deep Inelastic Scattering

- R. Cahn - CharlieFest

- January 27, 2006

## Quark-Parton Model

- k

- k’

- p

- p’

- q

- = fraction of proton’s momentum

*electron*

*parton*

- R. Cahn - CharlieFest

- January 27, 2006

## Bloom-Gilman Duality

- R. Cahn - CharlieFest

- January 27, 2006

## SLAC Theory Postdocs 1972

- Sir Chris Llewellyn-Smith

- John Ellis

-       Mike
- Chanowitz
- LBNL

- Frank Close
- Oxford

- Tony Hey
- Microsoft VP
- Technical Computing

- Bill Colglazier
- Executive Director
-  NRC

- Estia Eichten Fermilab

- Ling-Fong Li
- Carnegie-Mellon

- R. Cahn - CharlieFest

- January 27, 2006

## Electroweak Model

- R. Cahn - CharlieFest

- January 27, 2006

## Why Didn’t Electroweak Model Catch On?

- Dogma: “No neutral weak currents”
- BF
- BF
- Well, at least no strangeness-changing neutral weak currents.

- R. Cahn - CharlieFest

- January 27, 2006

## Asymptotic Freedom1973

- Llewellyn-Smith to RNC: “I told Feynman to read these papers while he was at a meeting in Hawaii.  When he came back he said,`That’s what I meant*: asymptotically *free.’ ”

- R. Cahn - CharlieFest

- January 27, 2006

## Electroweak Theory is Renormalizable

- R. Cahn - CharlieFest

- January 27, 2006

## Gargamelle Finds Neutral Currents (1973)

- Freon bubble chamber

*“**If the events are due to neutral currents, these two results are compatible with the same value of the Weinberg parameter, sin**2**** in the range 0.3-0.4”*

- R. Cahn - CharlieFest

- January 27, 2006

## SLAC Proposal 95 (1972)

- R. Cahn - CharlieFest

- January 27, 2006

## What is sin2W?

- SU(2)xU(1) has two couplings, g, g’
- Can’t predict sin2W
- SU(5) has one coupling.
- sin2W=3/8
- Wrong!
- Couplings evolve with mass scale

- R. Cahn - CharlieFest

- January 27, 2006

## Georgi, Quinn, Weinberg1974

- R. Cahn - CharlieFest

- January 27, 2006

## SLAC Proposal E-122 (1975)

**SLAC Proposal E-122 (1975)**

- R. Cahn - CharlieFest

- January 27, 2006

## Antecedents

- Jean-Baptiste Biot

- Louis Pasteur

*Optical activity of sugar solution*

*Separated mirror*
*Image crystals*

- R. Cahn - CharlieFest

- January 27, 2006

## Atomic Parity (non) Violation

- R. Cahn - CharlieFest

- January 27, 2006

## Photon-Z Interference in Deep Inelastic Scattering

- k

- k’

- p

- p’

- , Z

*electron*

*quark*

- R. Cahn - CharlieFest

- January 27, 2006

## Cahn & Gilman

- R. Cahn - CharlieFest

- January 27, 2006

## Asymmetry Formulae

- R. Cahn - CharlieFest

- January 27, 2006

## Graph for sin2w=1/3 from  Cahn and Gilman (1977) 

- Absence of parity violation in the atomic bismuth experiments suggested a vector coupling for the electron, i.e. the existence of a right-handed partner.

- R. Cahn - CharlieFest

- January 27, 2006

## End Station A

- 8 GeV
- spectrometer

- 20 GeV
- spectrometer

- R. Cahn - CharlieFest

- January 27, 2006

## Polarized Electron Source

- R. Cahn - CharlieFest

- January 27, 2006

## Experimental Set Up

- R. Cahn - CharlieFest

- January 27, 2006

## E122 Prism Rotation

- R. Cahn - CharlieFest

- January 27, 2006

## Measurement of Beam Polarization

- Magnetized iron:
- 7.8% of electrons
- polarized along beam

- 35% polarization

- R. Cahn - CharlieFest

- January 27, 2006

## Rotate Polarizer

- R. Cahn - CharlieFest

- January 27, 2006

## Rotate input photon linear polarization

- R. Cahn - CharlieFest

- January 27, 2006

## Spin Precession Depends on Energy

- R. Cahn - CharlieFest

- January 27, 2006

## Result from Experiment

- R. Cahn - CharlieFest

- January 27, 2006

## Measurements of sin2W

- R. Cahn - CharlieFest

- January 27, 2006

## E158 - Longitudinally Polarized Moller Scattering

- R. Cahn - CharlieFest

- January 27, 2006

## E122 and the Development of Particle Physics

- E122 played a decisive role in establishing the Standard Model and rejecting baroque alternatives.
- E122 set a standard for elegance and precision, an exemplar for all future high energy experiments.
- E122 continues to inspire fundamental measurements with polarized electron beams.

- R. Cahn - CharlieFest

- January 27, 2006

## Charlie’s Central Position in the Great Work of Our Field

- R. Cahn - CharlieFest

- January 27, 2006