Linear Collider Physics

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Linear Collider Physics

• Tohru Takahashi
• Hiroshima Univerisity

Aug. 10, 2000 3rd ACFA-LC WS Taipei
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Introduction
K.Fujii

• The First ACFA LC WS ,,,,,Beijing
• Justification is over.
• More
• detailed simulation
• for detector design
• with realistic beam related backgrounds
• theoretical insight
• to expand the potential of the collider

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• The Second ACFA LC Ws Seoul
• talks on detailed simulation
• theoretical insight
• The Third one has to see
• where we are toward the ACFA Report.

draft by the end of 2000 submitted in spring 2001
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Issues to be covered in the ACFA report

• Physics
• How well we can explore mechanism of the symmetry
  breaking?
• Higgs, SUSY, top, anomalous coupling, contact
  interaction,,,,,,,,
• Detectors
• good enough for precise measurement?
• tough enough with beam background?
• Options gg/ge, e-e-,
• Well justified?
• thechnically feasible?

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Physics to be explored

• mechanism of the electroweak symmetry breaking

LC has to find it, identify itself
something, called Higgs, somehow, condensed to
the vacuum
world we live,,,, electroweak superconductors
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Some scenario

• Promising?
• light higgs boson
• most lucky
• light higgs, Heavy Higgs, SUSYs
• Grand Unification
• ,,,,,,,,,,
• no higgs at LC lt 500 GeV
• strong coupling in Higgs sector

always have top, Ws
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Light Highs boson
A.Gurtu, ICHEP2000
Mh lt 175 GeV _at_ 95 C.L.
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If light higgs bosons

• Discovery seems ok

even in NMSSM
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Precise measuremt of Higgs property

• Once a Highs boson is discovered
• s(hz), Br(h-gtWW)
• Higgs gauge coupling
• branching ratio to fermion
• Higgs Yukawa coupling
• has information on heavy mass content
• CP
• SM, or exotic

Which/what highs it is.
w
h
h
z
z
w
mass
f
h
f
g
h
g
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Mass
Lhomann, LCWS99
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Branching Ratio etc
I.Nakamura, LCWS99
hep-ex/007022
only assuming
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two photon decay width

• ee-
• gg

Ohgaki,Watanabe,TT
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higgs coupling CP

• light h ee-
• gg
• Linear Polarization
• H,A interference

Kamoshita, Seoul
Asakawa, LCWS99
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If SUSY,,,,
Planc scale Physics
SUSY breaking
SUSY spectra coupling
SUSY Spectroscopy
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Example

W
W
e-R
e-R
ne
W0
W-
e
W-
e
WW background suppressed by pol beam!
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Demonstration of the measurements

• Chargino and neutrarino mass

jets
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Scalar muon mass
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Selectron production
ee-
e-e-
eg
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Test of SUSY GUT
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If no new particles

• Try to get information of physics of high energy
• which energy we have to go next
• Anomlous coupling of W bosons
• contact interaction
• Top quark property,,,,,,,,
• In other word,,,,,,,
• these physics are most promising in some sense

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Anomalous coupling of W bosons

• ee-
• gg
• do good a job up to 500 GeV

gg 10fb-1
gg 10fb-1
50fb-1
100fb-1
200fb-1
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contact interactions

• e-e- ,ee-

positron polarization?
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top quark physics
GD
GP
GD

• Promising
• does not depend on scenarios.
• large decay width allow us to see top decay
  properties

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next step

• more precise measurement
• testing CP in top production/decay
• requires full reconstruction of the top quark
  final state

ISR, beamstrahlung, missing P, top, W
width, b-tagging
a most tough test channel
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Detector-Beam related Issues

• Physics at the Linear Collider must be physics
  of precise measurement.
• 1) High energy interaction
• high energy narrower jets.
• high energy particles
• 2) High luminosity
• beam-beam interaction
• beamstrahlung
• incoherent pairs
• 1)2)
• hadronic background

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TeV Gravity
Moller
BhaBha
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Beam-Beam Interaction
A field of the bunch seen by an electron ,,,,,,
O(kT)
critical energy of synchrotron rad.
(beamstrahlung)
pair background
Lum dist.
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Tauchi, Beijing
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Interaction Region
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Effect of beam interaction

• beamstrahlung

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Interaction region
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Incoherent pairs
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Minimum veto angle

• pair production

acoplanar tau pairs
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Hadronic background

• resolved photon process
• bunch ID
• good t0 resolution of the CDC

overlap prob.
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Linear Collider options
scenario
ee-
gg/ge
e-e-
light Higgs only
SUSY
Strong int.
W coupling
WW scatt.
others extradimension,,,
better than ee-?
better than ee-?
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Summary

• Let see
• where we are toward the ACFA report
• we should fully explore the potential of the
  linear collier with possible options

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Effect on the Highs properties of a new physics