================================================================== MACHINE ISSUES ================================================================== Jym Clendenin e- polarization @ future collider current status of strained GaAs cathodes 85% achieved relatively independent of the parameters of the super lattices also optained 85% in routine operation for E158 85 to 90% seems a realistic electron polarisation for a LC Some projects to increase gun gradient either thorugh higher voltage in (pulsed) DC guns or by going to RF-guns. Physics studies: Use 85%, all necessary parameters have been reached. John Sheppard Undulator Positron Systems Positron polarization as an option in phase II of a future collider Systen layout for an undulator based source Without collimation of the photon beam expect around 50% positron pol. Collimating the photon beam increases the polarisation to 60% at a loss of intensity of about 25%. Physics studies: Use 60%. A lot of work needs to be done to get there, but we believe it can be done. Discussion: What is the best position for the positron source. At a fixed energy of 150 GeV or at the end of the linac? Do we need to be able to flip positron polarisation? Do we have to do it fast? Positron polarization cannot be flipped at the source. It is flipped with the spin rotators at the damping ring. Either a pulsed solenoid or a pair of solenoids which you use alternatively. Toshiyuki Okugi Recent Activity on Polarized Positron Experiment at KEK Photon beam produced by Compton backscattering of a CO2 laser on e- beam Continious development at KEK since 1995 Experiment at KEK-ATF on-going Found intensity and polarization of gamma-beam in agreement with expectation Advantage: low-energy e- beam sufficient Disadvantage: huge laser necessary Rainer Pitham Various Ways of Polarizing Electrons and Making Positrons A number of ideas for future projects on electron and positron sources ================================================================== POLARIMETRY ================================================================== Mike Woods SLD Polarimeter Review of the polarisation measurement at SLD Polarimeter achieved 0.50% precision at SLD realistic goal for NLC: 0.25% improve knowledge of analysing power, linearity, electronics noise at Giga-Z also the precise knowledge of the beam energy is crucial (50 ppm) Peter Schueler Compton Polarimeters for TESLA Suitable location for upstream polarimeter: -630 m to IP Alignment tolerances 50 murad, tight, but probably okay Statistical error negligible already after 1 sec Total estimated error 0.5 %, could probably be reduced to 0.25% Downstream polarimeter unrealistic, Compton electrons drowned in spent beam background. Discussion: How large are the depolarization effects? Luminosity weighted? Do we need up- and -downstream polarimeters? If we have a down-stream polarimeter you can always turn of the second beam and measure the undisrupted beam? Need a second polarimeter anyhow? Mike Woods Downstream polarimeter for NLC Chicane in the beam extraction line to sperate Compton electrons from the disrupted beam. Seems to work nicely with the electrons (main measurement) Measurement of Compton photons possible with second beam turned off. ================================================================== PHYSICS ================================================================== Gudi Moortgart-Pick Summary of Physics advantages with polarization Discussion: Gain in statistics from effective luminosity: How much of this gain is lost by machine setup time? How much would we loose by running the machine in the 'wrong' helicity configuration? Achim Can we construct a CP-odd observable just from the transverse polarisation vectors and the initial e+ or e- momentum without even reconstructing the final state? Mike Do we need to write anything about electron polarisation? Make the point that polarised positrons are not more difficult/expensive than unpolarised positrons. Will we be able to put all the contributions received into the document? Into an appendix? In their original length or do we shorten them? Title: The case for positron polarization? Thomas: Differentiate improved precision from improved statistics. Fig 5 includes both. Put Giga-Z as section 2.2.5 behind statistics. Change the title on 2.2.1. Triggers the question, what if there is no SUSY? Move part of section 2.2.3 into the introduction. Bring back Gudi's table. Background suppression: two examples one with new physics from gamma/Z showing the suppression of W+W- and one more exotic example. smuon-pair prod would be a good candidate. Individual contributions: Shorten them and put them in the main text. But be careful, there are too many SUSY topics in a row. Make it its own section: 'examples'.