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E CM bias in the presence of Beamstrahlung

E CM bias in the presence of Beamstrahlung. Arik Florimonte, UCSC Mike Woods , SLAC. WORKSHOP  Machine-Detector Interface  at the International Linear Collider Jan. 6-8, 2005 SLAC . Wakefields, Disruption and y-z Kink instability. Disruption parameter is ratio of

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E CM bias in the presence of Beamstrahlung

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  1. ECMbias in the presence of Beamstrahlung Arik Florimonte, UCSC Mike Woods, SLAC WORKSHOP Machine-Detector Interface  at the International Linear Collider Jan. 6-8, 2005 SLAC MDI Workshop @ SLAC

  2. Wakefields, Disruption and y-z Kink instability Disruption parameter is ratio of bunch length to focal length: Linac wakefields generate “banana” beam distortions (larger for NLC than for TESLA) NLC example TESLA example (larger for TESLA than for NLC) MDI Workshop @ SLAC

  3. Summary of ECM Bias studies w/ Beamstrahlung OFF E1 and E2 are beam energies measured by the energy spectrometers. (ISR and beamstrahlung are turned off for this study.) Wakefields + Disruption Y-Z Kink instability E-Spread + E-Z correlation + Y-Z Kink instability ECM Bias Summary of ECMbias MDI Workshop @ SLAC

  4. NLC TESLA Summary of ECMbias NLC’ MDI Workshop @ SLAC

  5. E1 and E2 are beam energies measured by the energy spectrometers. (ISR and beamstrahlung are turned off for this study.) Definition of ECMbias (Beamsstrahlung OFF) Definition of ECMbias (Beamsstrahlung ON) ECM for NLC-500 Vary cutoff energy from 480-495 GeV MDI Workshop @ SLAC

  6. MDI Workshop @ SLAC

  7. ECM Bias versus Vertical Offset of Colliding Beams MDI Workshop @ SLAC

  8. Study of distributions for i) ECM (cannot measure this) ii) E1-E2 (closely related to Bhabha acolinearity) NLC NLC w/ random-ordered energy NLC NLC w/ random-ordered energy Negligible difference in 2 distributions Clear difference in 2 distributions NLC NLC w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions NLC NLC w/ random-ordered energy MDI Workshop @ SLAC

  9. Study of distributions for i) ECM (cannot measure this) ii) E1-E2 (closely related to Bhabha acolinearity) TESLA TESLA w/ random- ordered energy TESLA TESLA w/ random- ordered energy Clear difference in 2 distributions Negligible difference in 2 distributions TESLA TESLA w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions TESLA TESLA w/ random-ordered energy MDI Workshop @ SLAC

  10. Study of distributions for i) ECM (cannot measure this) ii) E1-E2 (closely related to Bhabha acolinearity) NLC’ NLC’ w/ random-ordered energy NLC’ NLC’ w/ random-ordered energy Clear difference in 2 distributions Competing/cancelling ECM bias contributions NLC’ NLC’ w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions NLC’ NLC’ w/ random-ordered energy MDI Workshop @ SLAC

  11. Summary of ECMbias without Beamsstrahlung Summary of ECMbias in presence of Beamsstrahlung → Energy spectrometers and Bhabha acolinearity alone are not sufficient to correct for this bias. Need beam dynamics modeling and other input from annihilation data, disrupted energy measurements, … MDI Workshop @ SLAC

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