Write-Up: `Beam Polarisation at a LC'

The 'Polarisation Write-up' should be addressed to our HEP community and should give a comprehensive
overview about  theoretical, experimental and machine issues of beam polarisation and should stress our
physics case for the use of polarised beams at a LC. In particular it should summarise either the physics
cases but also the technical issues -- like generation, measurement and cost -- of polarised positrons and
should list the ongoing activities concerning beam polarisation at a future LC.

For each topic the contact persons of the editorial board are given and everybody who made a study with
regard to beam polarisation should contact these people himself. It is planned to have a draft in the end of June.


Authorship of this document does not mean that you have to write yourself -- but you can, of course --
but it would be highly appreciated that you at least inform the contact persons about your  study with key
points, references and main results.


  •    Proposal:

  •      I. Introduction:

             Theory: chirality<->helicity, definitions, conventions,history
             Beam polarisation as an analyzer for  the coupling structure
             Expected degree of polarisation at a future LC

         II. Physics with Polarisation:

             Electron polarisation only: quite short, good summary and list of references
                                                           Update (e.g. CP-violation   in tau  sector, news)
                                                           SM -> New Physics

              Contact: Herb  Steiner + Tac  Hirose

             Electron+positron polarisation:  Improved accuracy for effective polarisation, statistics
                                                                  Table with background scaling factors for  W and Z
                                                                   ( and S/B and S/sqrt{B})
                                                                   Few  examples from SM, Higgs, New Physics,....
                                                                   Susy background studies,...
                                                                   Effects of  radiative corrections in polarisation observables
                                                                   Implementation in Monte Carlo Generators                                                                              
            Contact: Uriel Nauenberg + Achim Stahl

              Positron polarisation essential for: Update,
                                                                         Susy studies ( chiral quantum numbers of selectrons, e.g.)
                                                                         Highest precision at GigaZ
                                                                        `Preparation for new physics searches'
                                                                         Try to make all studies more homogeneous

               Contact: Herb Steiner + Gudi

              Physics case for transverse polarisation: Sensitivity to longitudinal W-bosons
                                                                                    CP-violation phenomena
                                                                                    Effects in Susy and Extra dimension
                                                                                    Test of mixing matrices for Susy particles
                                                                                     Implementation in Monte Carlo Generators

                Contact: Tac Hirose + Tom Rizzo + Gudi

          III. Machine issues:

             Remarks about machine operation of polarised sources:    Loss of luminosity?
                                                                                                           Machine time for running-in
                                                                                                           Reduced intensity of positron beam?
                                                                                                           Increased energy spread?
                                                                                                           Order of magnitude of saved money?

             Electron polarisation:   History, results, short description of the hardware
                                                     New developements in gradient doping

               Contact: Tsutomu Nakanishi + John Sheppard + Mike Woods

               Positron polarisation:   Description of the hardware, possible schemes
                                                      Order of magnitude of additional costs
                                                      Helical undulator from the very beginning
                                                      Design and operation characteristics of spin rotators
                                                      Number of spin rotators
                                                      Plans/results from Cornell
                                                      Plans/results from Daresbury
                                                      Expected polarisation degree (E-dependence?)
                                                      Impact on lumi and energy spread
                                                      Description of E166: short description
                                                                                          physics potential: what does it tests?
                                                                                          for what is it essential?

                 Contact:  Klaus Floettmann + Tsunehiko Omori + Raner Pitthan + John Sheppard

                 Transverse polarisation:  short description of hardware
                                                           order of magnitude of additional costs
                                                           which R&D needed?
                                                           cost of spin rotators?

                  Contact:  Klaus Floettmann + John Sheppard

          IV. Polarisation Measurement:

              History, results
              Possibilities: Compton,  Moeller,  Bhabha
                                       Technical potential
                                       Pro's and Con's
                 Electron+positron polarisation: short description of the polarimeter
                 Polarimetry for transverse beam polarisations
                 Achievable precision
                 Polarisation transport and depolarisation in the IP
                 Polarimetry up- and/or downstream?
                 Technical possibilities at the LC designs
                 Polarimetry needed for E166

                 Contact:  Peter Schueler + Mike Woods

    Editorial Board: 'Polarisation dream team'

           Physics:         Tachishige Hirose, Uriel Nauenberg, Thomas Rizzo, Achim Stahl,
                                    Herb Steiner and myself
           Machine:      Klaus Floettmann, Tsutomu Nakanishi, Tsunehiko Omori,
                                    Rainer Pitthan, John Sheppard
           Polarimetry: Peter Schueler, Mike Woods

    Back to the  POWER homepage

    Last  update of this page: 25-August-03

    by Gudi