1 / 13

Polarimetry at NLC How Precise? e - e - 99 Workshop, UC Santa Cruz Dec. 10-12, 1999

Polarimetry at NLC How Precise? e - e - 99 Workshop, UC Santa Cruz Dec. 10-12, 1999. Mike Woods SLAC. Standard Model asymmetries in e + e - and e - e - testing for physics beyond SM polarimetry from SM asymmetries running at Z 0 resonance

asher-rose
Download Presentation

Polarimetry at NLC How Precise? e - e - 99 Workshop, UC Santa Cruz Dec. 10-12, 1999

An Image/Link below is provided (as is) to download presentation 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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Polarimetry at NLC How Precise? e-e- 99 Workshop, UC Santa Cruz Dec. 10-12, 1999 Mike Woods SLAC • Standard Model asymmetries in e+e- and e-e- • testing for physics beyond SM • polarimetry from SM asymmetries • running at Z0 resonance • Other considerations for precision polarimetry • background suppression of W pairs in e+e- • depolarization in beam-beam interaction • design of extraction line and beam losses

  2. Assumptions for Machine Performance Parameter e+e-e-e- 500 GeV 500 GeV 80 fb-1 25 fb-1 P1 0 90% P2 90% 90%

  3. SM Asymmetries in e+e- From Snowmass ‘96 study, Consider, Final State #events ALR W+W - 560K 100% q q 250K 45% 0.005 l+l- 120K 10% 0.032

  4. SM Asymmetries in e+e- From Snowmass ‘96 study, Consider, Final State #events ALR W+W - 560K 100% q q 250K 45% 0.005 l+l- 120K 10% 0.032

  5. e- W- n W+ e+ SM Asymmetries in e+e-(cont.) • Notes: • 1. Better than 1% polarimetry is needed to fully exploit • these measurements for SM tests. • 2. Can we use asymmetry in forward W pairs as a polarimeter? • Yes, if can achieve backgrounds below 1%. • (This level of backgrounds is achieved for LEP200 W mass • measurements, if require one W to decay to ee or mm.) • advantage wrt Compton polarimetry is that any • depolarization in beam-beam interaction is properly • accounted for • disadvantage wrt Compton polarimetry is Compton can • achieve 1% accuracy in a few minutes

  6. SM Asymmetries in e-e- e-e- to determine: From F. Cuypers and P. Gambino, Phys. Lett. B388: 211-218, 1996, Measure 3 asymmetries: Consider, For comparison, i) SLD has achieved ii) E158 at SLAC will achieve (at Q2=0.02 GeV2)

  7. SM Asymmetries in e-e- (cont.) Notes: 1. Achieves better than 1% polarimetry using a SM physics asymmetry. Again, has advantage wrt Compton polarimetry that it properly takes into account any depolarization due to beam-beam effects. But disadvantage is that Compton can achieve 1% accuracy in a few minutes.

  8. The Linear Collider Z-factory option Some anomalies remain from the LEP/SLC era (sin2qWeff, Ab, Nn) May be very desirable to accumulate a large Z sample (>>10M) with polarized beam(s) (ex. Monig and Hawkings, DESY-99-157) Ideally the positron beam has P+=0.6, and can then use Blondel scheme for polarimetry from the measured physics asymmetries in the detector. However, if positron beam is unpolarized then will want a very precise Compton polarimeter, better than the 0.5% accuracy achieved with SLD’s Compton. And will want the Compton to measure any beam-beam polarization effects.

  9. Other Considerations for Precision Polarimetry 0 2.4% 1% 2.6% 2% 3.1% • Background suppression of W pairs in e+e- • most important is to achieve high polarization; • increasing P from 80% to 90% allows for a • factor 2 further background reduction • need more precise polarimetry as P increases An example P =90% Observe 400 events -- after analysis cuts, but no polarization cut Observe 40 events -- after additional requirement on polarization state An excess of 20 events is observed above the expected W pair background. Would like 1% polarimetry in order to achieve a 4s signal.

  10. Depolarization in beam-beam interaction • need Compton polarimeter in extraction line to measure • polarization with and without collisions, or • polarization measured from a physics asymmetry • need to emphasize that depolarization should be included in • parameter tables for the Interaction Region • need to encourage the simulation programs Guinea-Pig and • CAIN to include polarization effects

  11. But • Design of Extraction Line; effect of beam losses • ideally, want to have a large number of diagnostic devices for • measuring and optimizing luminosity, • polarization and energy measurements • in practice, need to balance this with cleanly transporting the • beams to the dumps. Want to minimize beam losses • and backgrounds for the detector. • ZDR approach allowed for a Compton polarimeter, a wire scanner and • other devices • Increased disruption effects in higher luminosity schemes or e-e- option, • may lead to elimination of some extraction line diagnostics • important to point out how this may limit the physics capability • important to still try to incorporate polarization and energy diagnostics • in the extraction line

  12. Summary Standard Model asymmetries - better than 1% polarimetry is needed for testing SM and probing for new physics - SM asymmetries in e-e-e-e- and in e+e-W+W- should achieve better than 1% polarimetry (very good detector coverage and capability needed for forward angles) Other considerations for precision polarimetry - should have a Compton polarimeter in the extraction line - depolarization effects should be calculated in beam-beam simulations and tabulated in IR paramater tables - high luminosity scenarios and e-e- option significantly complicate the design for a Compton polarimeter in the extraction line, and could make it impractical

More Related