Calibration of the MINOS Detectors for Calorimetry

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Calibration of the MINOS Detectors for Calorimetry

• Jeff Hartnell
• University of Oxford
• Rutherford Appleton Laboratory
• Annual APS April Meeting 2004

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Talk Outline

• MINOS Neutrino Physics and Calibration Targets
• Near, Far and Calibration Detectors
• Calibrating the Calorimeter
• Results from the Calibration Detector
• Stopping Muons Our Standard Candle
• Setting the Relative Energy Scale Between all 3
  Detectors

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MINOS Neutrino Physics and Calibration Targets

• Compare Near and Far neutrino energy spectra.
• Looking for nm disappearance as a function of
  energy the dip.
• Very important that we can accurately reconstruct
  the neutrino energy.
• Will hopefully have statistics for a measurement
  of Dm2 to a few percent.
• Have a target of 5 for the absolute energy
  calibration.
• Require that the relative calibration between
  detectors is 2.

Near
Far
Ratio Far/Near
?m2
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3 MINOS Detectors (Near, Far, Calib.)

• Common features
• Alternating steel-scintillator, magnetised,
  tracking calorimeters.
• WLS fibre-optic cables to extract the
  scintillator light.

Far Detector plane under construction
Calibration detector not magnetised
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Calibration Detector at CERN (CalDet)

• Small version of Near and Far detectors
• Exposed to m, p, e, p beams of 0.2-10 GeV
• Hadronic EM energy response
• Tune the MC

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Calibrating the Calorimeter for Shower Energy
Reconstruction

• Problems
• PMT gain drift and non-linearity.
• Scintillator output varies from strip to strip
  (14 RMS) .
• Light output depends on particle type and
  particle energy.

Solutions Measure using light-injection syste
m Normalise using cosmic muons. Measure
response of particles of known energy using
the Calibration Detector. Characterize in
MIPs/GeV. (MIPMinimum Ionizing Particle)
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CalDet Results Shower Response and Resolution

• CalDet data all taken have5 months integrated
  beam time.
• Analysis now in final stages.
• Detailed MC comparison and tuning switched to
  using GCALOR for hadronic shower modelling.
• Particle energy scale measured to 1-2.

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Use Stopping Muons to Extrapolate CalDet Results
to other 2 detectors

• Stopping muons give us a calibration source of
  known energy - a standard candle.
• Cant use through-going cosmic muons since energy
  spectrum (and hence energy deposition) is
  different for all 3 detectors and not known
  accurately enough.
• Working backwards from the end of a stopping muon
  track you know its energy Use to define a
  standard signal unit MIP (Minimum Ionizing
  Particle).
• Stopping muons are the same at all 3 detectors!

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Stopping Beam Muons in CalDet (at 1.8 GeV/c)
Beam Direction
Corrected ADCs
Relativistic rise in ionisation 10
Muons stop here
Plane
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Track Window Method

• Want a method that is inherently robust and not
  sensitive to reconstruction problems.
• Sum up the energy deposition in a window located
  a fixed distance from the end of the track.
• Define a Minimum Ionizing Particle (MIP) to be
  the average energy deposited in the window by a
  perpendicular muon in one detector plane.

Many muons low statistical error (0.2)
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Relative Calibration Results at CalDet
Before Stopping Muon Calibration
After Stopping Muon Calibration

• Use 1.8 GeV electrons from test beam
• Different electronics and PMTs used in two cases.
• Gives an arbitrary difference in the ADC scale.

0.5 difference in response
Sum of MIPs in Event
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Conclusion

• MINOS requires neutrino energy scale correct to
  5.
• Particle energy scale measured to 1-2 with
  CalDet.
• Stopping muons at CalDet
• Relative energy calibration works
• Demonstrated to lt2.
• To be done
• Transfer energy scale to the other 2 detectors
• Must be the same within 2.

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The End!