1. ILC Meeting Vancouver July 20061 What Does Beam-strahlung Tell Us? William Morse - BNL

2. ILC Meeting Vancouver July 20062 Achieving the Design Luminosity Will Be a Challenge Bunch P - (t) {N, E, x, y, z,  x,  y,  z,  xy,  x,  y } Bunch P + (t) {N, E, x, y, z,  x,  y,  z,  xy,  x,  y } Instantaneous Luminosity: x y

3. ILC Meeting Vancouver July 20063 Run Time Measurements Beam-beam deflections (pickup electrodes) Beam-strahlung gammas (GamCal) Beam-strahlung pairs (BeamCal) We need robust and complementary information

4. ILC Meeting Vancouver July 20064 Beam-strahlung F = e(E +  B). B max  1KT Instantaneous power radiated: P   3% P e N   1.5N e Bethe-Heitler:  e → e e + e -  BH  38 mb  1GeV Landau-Lifshitz: ee → ee e + e -  LL  19 mb  0.15GeV Other processes much smaller C. Rimbault et al., Phys Rev ST AB 9,034402 (2006).

5. ILC Meeting Vancouver July 20065 Bethe-Heitler Pairs  e → e e + e - For left and right detectors separately: N + /  x  y and N - /  x  y. Question: How well does this really work? Answer: Needs simulation.

6. ILC Meeting Vancouver July 20066 Landau-Lifshitz Pairs ee → eee + e - For left and right detector equally 1 GeV

7. ILC Meeting Vancouver July 20067 Simulations W. Morse (BNL) W. Lohman and M. Ohlerich (DESY Zeuthen) Submitted as an ILC Note Guinea Pig simulations varying some of the 500 GeV ILC bunch parameters around nominal values

8. ILC Meeting Vancouver July 20068 Vertical offset E BeamCal (TeV)

9. ILC Meeting Vancouver July 20069 Vertical Offset R (10 -6 )

10. ILC Meeting Vancouver July 200610 Bunch Width BeamCal E (TeV) R 10 -6

11. ILC Meeting Vancouver July 200611 Comparison Sign of dE/d(bunch characteristic) at design values. Note that all five lines are different, which means complementary information. ParameterPairsGammasRatio X offset0 (max) zz -- 00 yy 00 xx --- Y offset0 (max)0 (min)0 (max)

12. ILC Meeting Vancouver July 200612 Bunch Height

13. ILC Meeting Vancouver July 200613 Bunch Length

14. ILC Meeting Vancouver July 200614 Is There More Info in BeamCal? T.Tauchi,K.Yokoya Phys Rev E51,6119(95) 6<r<7cm azimuthal dist But, Moliere dia.  2cm! Also,  1 Bhabha/BX! Thus we need more simulation to show that it is robust enough.

15. ILC Meeting Vancouver July 200615 Radiative Bhabha Detector? After TESLA quadrupole magnet (ILC space issues) O. Napoly and D. Schulte, Luminosity Monitor Studies for Tesla DESY TESLA 97-17: “Because of its sensitivity to the beam- beam effect, the radiative Bhabha signal within a fixed kinematical acceptance is no longer proportional to the luminosity.”

16. ILC Meeting Vancouver July 200616 GamCal Design Can we only measure the large angle (  1mrad) gammas? Too sensitive to the beam-beam effect 0.1GeV/250GeV = 0.4mrad Just started thinking about detector design (BNL-Yale). Collect Cerenkov light from H 2 O Dump?

17. ILC Meeting Vancouver July 200617 Clever Idea: Measure Polarization Vector of Visible Beam-strahlung Light

18. ILC Meeting Vancouver July 200618 Being Tested Now at CESR CESR Detector  = 11.5 mrad (  z  12mm) ILC  z  0.3mm, ie. much shorter than CESR

19. ILC Meeting Vancouver July 200619 Robust and Complementary DetectorX offsetY offset xx yy PUE xx yy Normal E GamCalLowHighLowNormal E BeamCalLow Luminosity, ie. R, is low. Note that all columns are different, ie. complementary information.

20. ILC Meeting Vancouver July 200620 Conclusions We need robust, redundant information: Beam-beam deflections Beam-strahlung gammas Beam-strahlung pairs E(pairs)/E(gammas) particularly valuable Largely proportional to instantaneous luminosity We need a “White Paper”, in my opinion.

21. ILC Meeting Vancouver July 200621 Extra Slides

22. ILC Meeting Vancouver July 200622 1  21  2 + - y z

23. ILC Meeting Vancouver July 200623 Can We Correct? Needs more study.

24. ILC Meeting Vancouver July 200624 Perfect Collisions