Polarization at the Linear Collider


Polarization will play a crucial role at the Linear Collider for interpreting new physics signals and for making precision measurements.  Backgrounds to new physics reactions can be reduced by choice of the electron polarization state.  The origin of new physics reactions can be clarified by measuring their polarization-dependence.  The baseline designs for the NLC/JLC and TESLA machines provide for polarized electron beams with Pe~ 80-90% expected.  Initially the positron beams will be unpolarized, but there is significant interest and physics motivation for achieving polarized positron beams in future upgrades.

The following is a list of  topics, questions and some references. Suggestions are welcome!

Physics Questions

  • What precision for polarimetry is required?
  • Can W-pairs be used for polarimetry?
  • Which physics measurements drive the polarimetry requirements?
  • What depolarization is expected from the beam-beam interaction and what are its characteristics?

Operational Questions

  • What is the possible variance of polarization on short time scales?
  • How precise do we need real-time measurements (pulse to pulse or train to train)?
  • What are the likely correlations with other parameters (energy, luminosity)?
  • What are the backgrounds in the polarimeter detector
  • Does the polarimeter create backgrounds for the IP Detector?

Potential Beam Instrumentation

  • Compton polarimeter before IP
  • Compton polarimeter after IP
  • Mott polarimeter at source
  • Damping Ring polarimeter using synchrotron radiation

Potential Detector Measurements

  • W-pairs
  • SM asymmetries from Bhabhas etc. if both beams polarized ala Blondel technique



Last Updated:  April 17, 2002