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E CM bias in the presence of Beamstrahlung PowerPoint PPT Presentation


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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, 2005SLAC . 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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ECMbias in the presence of Beamstrahlung

Arik Florimonte, UCSC

Mike Woods, SLAC

WORKSHOP Machine-Detector Interface  at the International Linear Collider

Jan. 6-8, 2005SLAC

MDI Workshop @ SLAC


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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


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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 + DisruptionY-Z Kink instability

E-Spread + E-Z correlation + Y-Z Kink instability ECM Bias

Summary of ECMbias

MDI Workshop @ SLAC


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NLC

TESLA

Summary of ECMbias

NLC’

MDI Workshop @ SLAC


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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


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MDI Workshop @ SLAC


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ECM Bias versus Vertical Offset

of Colliding Beams

MDI Workshop @ SLAC


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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


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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


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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


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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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