Physics Motivation

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Physics Motivation Measurement from
Annihilation Data

• Tim Barklow
• SLAC
• Machine-Detector Interface at the ILC
• January 8, 2005

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Lumi, Energy Measurement Goals

• Luminosity, Luminosity Spectrum
• Total cross sections absolute dL/L to
  0.1
• threshold scans core width to lt0.05 Ecm
  50 sEcm
• and tail population dL/L to lt 1

• Center of Mass Energy
• Smuon mass 1000 ppm (24 Mev for 220
  GeV smuon)
• Top mass 200 ppm (35 Mev)
• Higgs mass 200 ppm (60 MeV for 120 GeV Higgs)
  

The optional Giga-Z program requires better
precision for luminosity and beam energy
measurements, such as dEcm/Ecm 50 ppm for a 5
MeV W mass or 10-4 (absolute) ALR measurement.
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Beam Energy Profiles
Lumi Weighted
After Collision
Before Collision
Ebeam (GeV)
Ebeam (GeV)
Ebeam (GeV)
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E-Z Cor, Y-Z Kink Instability and ECM Bias
Wakefields Disruption Y-Z Kink
instability
E-Spread E-Z correlation Y-Z Kink
instability ECM Bias
Summary of ECMbias at s 500 GeV
ltECMbiasgt (Dy 0) s(ECMbias) (Dy 0) Max(ECMbias) vary Dy, hy
50 ppm 30 ppm 250 ppm
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ILC-500
Summary of ECMbias
LC Machine Design ltECMbiasgt (Dy 0) s(ECMbias) (Dy 0) Max(ECMbias) vary Dy, hy
ILC-500 50 ppm 30 ppm 250 ppm
NLC'-500 0 ppm 10 ppm 50 ppm
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Simdet Detector Simulation of ee- ? Zh
Recoil Mass Statistical Error
Recoil Mass (GeV)
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Statistical Error
Muon Energy (GeV)
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Statistical Error
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Ecm Measurement
(warm width)
(3X warm width)
Measurement
Tracker resolution at 150 400 mrad, together
with FSR and disruption effects, give dqa0.2
mrad
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Physics Error Summary

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• Methods for improving luminosity-weighted ECM
  Measurement
• Continue to use energy spectrometers and Bhabha
  acollinearity, but correct
• for energy bias by modelling the
  beam-beam interaction.
• Change RF Phase Profile in Accelerator
• Use Annihilation Data
• i) gZ, ZZ and WW events use existing Z and W
  mass measurements
• ii) utilize Bhabha energies in addition to
  Bhabha acolinearity
• iii) m-pair events use momentum measurements
  for the muons

These techniques should work well to achieve lt
200 ppm precision on ECMlum-wt
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Simdet Detector Simulation of
Recoil Mass Squared
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Select events with hard photons using lepton
angles.
momenta angles
angles only
Measured Ecm assuming recoil mass 0
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Summary

• 200 ppm Ecm uncertainty leads to a 30-50 MeV sys
  error for masses, with the exception of a 200 MeV
  error for the Higgs mass using the recoil
  technique.
• More studies are required to determine required
  precision on lumi spectrum. Initial estimates of
  a 1 precision need to be reviewed.
• In contrast to LEP2, track momenta may be as
  useful as angles for measuring Ecm with physics
  events. Beam energy and differential lumi
  measurement considerations might well drive
  tracker momentum resolution spec.