Tohru Takahashi

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8/29/2002LCWS02
??Technology and Machine Constraints

• Tohru Takahashi
• Graduate School of
• Advanced Sciences of Matter
• Hiroshima University

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Contents
JLC-gg option
(JLC NLC )

• Machine Parameters
• difference from ee-
• Lasers -
• gg collider w/ ee- beam
• Luminosity
• beam background,,,
• e-e- mode
• w/ ee- parameters
• optimization
• beam switch over

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Principle of gg, eg Collider
e beam
ip
laser
d
e250GeV e100GeV
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Beam parameters
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Effect of Electron Polarization
PL100
Leff
Pe100
1.0
Pe 90
0.93
Pe 80
0.87
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Beam Crossing angel is large
laser
e-
e-
large Beam crossing angle
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IR design
NLC
30mr
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Is a gg collider w/ the ee- beam really
impossible?

• why
• no beam switch over needed
• however, e-e- collider does
• no switching time needed
• want bunch-bunch switching?
• Positron polarization 50
• reduce luminosity?
• beam-beam interaction
• spent electrons?
• incoherent pairs?

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gg Luminosity e-e- vs ee-w/ JLC gg
param(rounder beam)
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Pt distribution of incoherent pairs( for all
paris)
of particlec/bunch
ee- gg param(round beam)
ee- collider(flat beam)
e-e- gg param(round beam)
Pt (Gev)
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Luminosity of e-e- collider

• Hd lt 1 due to anti-pich effect

• Disruption anlge ee- collider

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e-e- luminosity
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Optimizing e-e- luminosity
cf K.Thompson e-e- 99
e-e- HD w/ JLC ee- parameter
possible
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Summary

• Machine constraint gg collider
• beam crossing angle
• gg operation w/ ee- beam
• e- e- beam is preferable, however
• it is possble w/
• e polarization
• flat beam
• can not goto higher lum.
• e-e- collider
• 0.3Lee- possible w/ parameter optimization

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Machine constraint for gg and e-e-
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Pt distrubution of pairs (for vertex det.)
of particlec/bunch
Pt (Gev)
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Spent Electrons
e-e- beam
ee- beam
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e- beam parameters
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Interaction Region
NLC ZDR
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spent electrons, pairs by beam beam
interaction
low energy pairs
Even with large geometric luminosity
KEK report 97-17
beam beam effect is moderate thanks to e-e-
collision
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Luminosity Simulation (CAIN)
w/ JLC gg parameter
L(cm-2s-1/20GeV)