Machine Detector Interface Summary

1. Machine Detector InterfaceSummary Junji Haba, KEK

2. Beam background • Another very important issue in a high luminosity machine other than L. • Where it comes?.

3. What is beam background?

4. 10% occupancy means 10k ch has unnecessary hits!

5. Types of Accelerator Backgrounds • Synchrotron Radiation (SR) • Lost beam particles (BGB) • Touschek scattering • Luminosity backgrounds Nice introduction for non machine physicist. M. Sullivan

6. Lifetime Effects Different view from Machine operation • Quantum lifetime • (Not a problem as the RF voltage is high.) • Residual gas • Bremsstrahlung • Elastic scattering • Small change as the gas is only a few times worse. • Touschek effect • Luminosity • Bhabha (e+e-  e+e-) • Radiative Bhabha (e+e-  e+e-g) • Beam-beam tune shift J. Seeman

7. Synchrotron radiation from up/down stream Off momentum/orbit beam particle

8. Study of Touschek Effect Smaller beam-size (larger density)  larger background Touschek contribution < 20 % at collision ~ 50 % at single beam 31 % in simulation Touschek contribution must be corrected What we learn here is beam is different for collision. If no Touschek Collision run Single beam run O. Tajima

9. Touschek lifetime versus RF voltage Smaller bunches Quantum lifetime J. Seeman

10. Luminosity backgrounds M. Sullivan • Radiative Bhabhas These are initial state radiation events. In single ring colliders, these events were buried in the beam envelope and were eventually lost when the beam went through a bending magnet, many meters from the detector. The 2 ring B-factories, with shared quadrupoles and bending magnets closer to the IP, these events come out of the beam envelope much sooner and can be a source of detector background. • Touschek scattering at the IP? Touschek scattering ~1/sxsy . For PEP-II, given the Touschek lifetime to be about 400 min and the average beta x, y around the ring is ~30 m and that the IP betas are 0.3 and 0.012 we find a Touschek scattering enhancement at the IP of 1580. Normalized by length (1cm vs 2200 m) we get the IP rate to be ~7e-3 of the ring. For a 2A beam then there are ~1107 Touschek events per second at the IP from the LER. This is a very crude calculation and we need to check this guess with a full blown simulation. Seem very serious for PEPII as Luminosity grows up!!

11. M. Sullivan

12. Background parametrization based on February 2002 data Clean example from BaBar The observed background is roughly twice larger than the sum of the single beam contributions G. Wormser

13. SVT Background from HER HER sensitive SVT module (Does not have threshold shift problem): (BW:MID) Background almost doubled after move to half-integer Again it has come down a bit during run-4 Note peak occupancy is 150% higher than average occupancy! Degradation of the detector itself Moves toward half-integer Another type of background, not on luminosity nor on beam current For occupancies in all SVT modules, see: http://www.slac.stanford.edu/~babarsvt/SectionOccupancies.ps G. Wormser

14. It was noted that it may be difficult to distinguish “beam-beam” effect from “luminosity” background. • KEKB experience: “beam-beam” effect make HER beam size larger and hit the smallest acceptance of the ring resulting increase of background.

15. What is wrong with the background? 1)Degradation of the detector itself. • Light yield of scintillation crystal • Gain drop of DC wire • Damage in the readout electronic 2)High occupancy degrades the event reconstruction also. 3)Very high data trasfer rate

16. Gain drop in DCH (BaBar) Still can survive for while by rasing HV H. Kelsey

17. Light yield reduction in CsI (BaBar) as long as 10^34 operation M. Kocian

18. Also in Belle 1/10 though. cf Belle ECL By A. Kuzumin

19. Synchrotron radiation from HER upstream magnets. This killed SVD 1.0 Gain drop in Belle SVD Limits were set to the HER magnets. SVD1.1 60% gain drop in 5 days SVD 1.1 SVD 1.4 SVD1.4 25% gain drop in 1.5 years The downstream chamber was replaced with a Cu chamber S. Stanic

20. Resolution degration with occupancy Current operation Why we have very smallest beam pipe with very high background???? G. Wormser

21. Reconstruction efficiency of D* is really degraded seriously under high background Example in G. Wormser

22. Decrease of hits @ x20 occupancy Senyo • The electronics(Shaper/QT)deadtime is clouding out proper track hits under the high occupancy. Thus tracking efficiency and resolution depend on the readout system. More proper hits to reconstruct a track! Deadtime = 2200ns Deadtime = 600ns

23. Larger dead time. Greater loss of luminosity!

24. Do we understand the current beam background? • G. Wormser from BaBar • O. Tajima from Belle • S. Stanic form Belle

25. Monitoring system for SVD2 • The conceptual design remained the same as for SVD1.4, however, we changed many things: • New types of “monitoring hybrids”, specially designed for SVD2.0 IR kRad range RadFET RTD temp. sensor Low Gain PIN for Beam Abort Interlock High Gain PIN for monitoring/logging 1st layer RadFET/PIN/Pt100 hybrids Monitor tool is very important! S. Stanic 2nd and 3rd layer RadFET/Pt100 hybrids

26. Conclusions for short term issues • We have to look far ahead: Minimum 3 years • Look for worst case scenarios! • Look for end-product effects! • BABAR issues • Immediate concerns: SVT ATOM chip, IFRForward endcap • Next on-line: DCH DAQ • Longer term issues: SVT and EMC in 2008 • Changes in background issues • Beam-beam tails • injections • trapped events

27. Conclusions for short term issues • We have to look far ahead: Minimum 3 years • Look for worst case scenarios! • Look for end-product effects! • BABAR issues • Immediate concerns: SVT ATOM chip, IFRForward endcap • Next on-line: DCH DAQ • Longer term issues: SVT and EMC in 2008 • Changes in background issues • Beam-beam tails • injections • trapped events

28. Extraction SR in HER Single Beam HER Particle SR 50 mA 200 mA 100 mA Cool work! Hard-SR simulation 400 mA 600 mA 800 mA O. Tajima

29. Simulation gives an extremely good expectation! translated differently as Unbelievable ! (Karim) I don’t believe it (Steve, O)

30. Radiation Dose at SVD 1st layer At Maximum Currents: HER 1.1A, LER 1.6A (…) is simulation @ 1nTorr pressure Simulation gives an extremely good expecttion! which can be translated as Unbelievable ! (Karim) I don’t believe it (Steve, O) • We can trust simulations • Its uncertainty for abs. may be factor a few Touschek contribution is reduced based on measurement O. Tajima Data and simulation is consistent

31. What background expected for the superBfactory? • Good understanding of current background is being establisehd. • Serious simulation study just started. • Very high background extrapolated from the current experience (BaBar). • Degradation may be manageable(BELLE).

32. Serious study Just started with reallistic lattice K. Trabersi

33. 10 times higher. Smaller than they assumed in the detector design. 1 MRad/yr 100 kRad/yr K. Trabersi

34. Slight modification of Q magnet position easily changes the dose! K. Trabersi

35. Very simple extrapolation. Is it OK to design the next detector beased on it?

37. Slow p efficiency from BD*(Dpslow)p Senyo • About 80% of efficiency is kept in the slow p efficiency under x20 occupancy. • Need higher efficiency to keep full reconstruction eff. recon. eff. of the slow pion ~ single track efficiency of slow p BD*p reconstruction eff. including geometrical acceptance

38. Vertex resolution w/ BJ/KS Vertex resolution is kept less than 160mm (ZCP-Ztag) Senyo

39. M. Kocian

40. PEPIII may be very similar to KEKB, that is simple extrapolation has no meaning!!

41. HER-beam HER-beam Idea for Hard-SR reduction Possible headache for KEKB-type IR design. SR If we can bend beam  photon-stop far place SR If 2 times far place  1/4 BG O. Tajima

42. Injection • Continuous Injection (trickle ) is necessary to keep the peak luminosity. • To maximize the efficiency, switching injection pulse by pulse (LER<->HER) is very interesting.

43. Lifetime for 1036 luminosity We can’t live without a continuous injection anyway. J. Seeman

44. Beam pipe issue (today) • Can we have smaller beam pipe ? • Sullivan, • SR, I^2R, and HOM ?? Many technical obstacles…. • Katayama • Beam is flat. Why not flat beam pipe? • What we can get with extremely flat beam pipe.

45. Side view of S-F beam pipe Ｖａｃｕｕｍ or accelerator components (nano beta??) Ｓｉｌｉｃｏｎ　ｖｅｒｔｅｘ　ｄｅｔｅｃｔｏｒ　（３００mm thick) Beryllium beam pipe (500mm) 1.6 cm N. Katayama

46. N. Katayama S-F geometry vs current geom. Perfect reconst. Bs mixing, BDtn etc Error on flight distance (mm) Error on flight distance (mm) See difference in scale

47. Summary of summary • Many studies just started with the 0th version of IR design • It’s too simple-minded to design the detector based on the straight extrapolation from now. • Hope to discuss in the next WS also on mechanical interface btw detector and machine like support, heat treatment around beam pipe, concept of IR assembly….