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Timing and Bunch Structure

Timing and Bunch Structure. Warm-Cold Differences and Possible Implications Background Characteristics Hadronic Background: Impact on Physics. Klaus Desch, University of Hamburg LCWS04, Paris, 20/04/04. Time Structure of the Beams. Possible Implications: Overview.

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Timing and Bunch Structure

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  1. Timing and Bunch Structure • Warm-Cold Differences and Possible Implications • Background Characteristics • Hadronic Background: Impact on Physics Klaus Desch, University of Hamburg LCWS04, Paris, 20/04/04 1

  2. Time Structure of the Beams 2

  3. Possible Implications: Overview • Short Bunch Distance for warm: pile-up in the detector? •  low occupancy in main detector •  time-stamping sufficient (rest of this talk) •  forward calorimetry has high occupancy •  1BX readout needed (see talk by T.Tauchi) • Long Bunch trains for cold: •  need to readout vertex detector a few times during the train •  pick up noise? 3

  4. Time-Stamping: how much pile-up can we afford? Physics has to give the answer. At LCWS04: physics studies for overlaid background from America, Asia and Europe Additional energy inthe detectorfrom   hadrons: 4

  5. 64BX 0BX 18BX 2. Hadronic Background HZbbqq event(500 GeV, mH=120 GeV) 5

  6. Physics impact 1: Higgs mass measurement Higgs mass measurement in hadronic channel bbqqKinematic constraints can be appliedOptimization of algorithm partly recuperates effects from background Comparison of results: Imhof,Meyer,Raspereza,KD Abe,Barklow,Jaros 6

  7. Physics Impact 2: CP study in Hττ Exclusive reconstruction of Hττ+0-0 Background photons may spoil tau reconstruction: Imhof 20BX 40BX 7

  8. Physics Impact 3: Higgs in WW-fusion @ 500 GeV e+e-H : no kinematic constraints, Higgs mass estimator = visible mass Huge distortion, need cleaning cuts against background clusters without pt cut Yamashita,Kanzaki 8

  9. Physics Impact 3: Higgs in WW-fusion @ 1 TeV Effect of pt cut on signal and on dominant (ZZ) background: Meyer 9

  10. Physics Impact 3: Higgs in WW-fusion @ 1 TeV normalized to 1BX@TESLA / 2.5BX at NLC 10

  11. What can be achieved? Tracking: Studies indicate 2-5 ns track timing possible in principle for TPC and SiDetailed time-dependent simulation needed – non-trivial Calorimetry (most important in central detector, many neutrals): With electronics inside Si-W calorimeter 5ns for single cells achievable in SLAC designAveraging over 30 hits: 5 ns / sqrt(30) = 1 ns (Jaros, Frey) Concerns: - Distribute o(GHz) clock over a large detector- Timing calibration for o(108) cells (o(105) r/o chips) to ns precision- Cluster finding to do the averaging – need detailed time-dependent simulation- Charged particles in endcap: time-of-flight correction (loopers!) 11

  12. Preliminary Summary • Integrating the hadronic background from more than a few bunch-crossingshas a sizeable impact on the physics performance • America, Asian, and European studies agree • At NLC, a bunch tagging of few ns is needed to become comparable to theTESLA situation • R&D on detector timing is vital for warm technology • Timing capability adds complexity – how much? 12

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