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Calibration of the MINOS Detectors Using Stopping Muons. Jeff Hartnell University of Oxford & Rutherford Appleton Laboratory IoP Particle Physics 2004 Tuesday 6 th April. Talk Outline. The MINOS Experiment Near, Far and Calibration Detectors Calibrating the Calorimeter

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calibration of the minos detectors using stopping muons

Calibration of the MINOS Detectors Using Stopping Muons

Jeff Hartnell

University of Oxford &

Rutherford Appleton Laboratory

IoP Particle Physics 2004 Tuesday 6th April

talk outline
Talk Outline
  • The MINOS Experiment
  • Near, Far and Calibration Detectors
  • Calibrating the Calorimeter
  • Stopping Muons: Our Standard Candle

Jeff Hartnell, IoP Particle Physics 2004

minos neutrino physics
MINOS Neutrino Physics
  • Long-baseline neutrino oscillation experiment.
  • 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.

Near

Far

Ratio:

Far/Near

Jeff Hartnell, IoP Particle Physics 2004

calibration targets
Calibration Targets
  • Will hopefully have statistics for 10% measurement of Dm2.
  • Have a target of 5% for the absolute energy calibration.
  • Require that the relative calibration between detectors is 2%.

Δm2

Jeff Hartnell, IoP Particle Physics 2004

minos detectors x3
MINOS Detectors (x3)
  • Common features:
    • Alternating steel-scintillator, magnetised, tracking calorimeters
    • WLS fibre-optic cables to extract the scintillator light

Far Detector plane

under construction

Jeff Hartnell, IoP Particle Physics 2004

near detector
Near Detector

Breaking News

First Plane Installed:

31st March 2004

Jeff Hartnell, IoP Particle Physics 2004

calibration detector at cern caldet
Calibration Detector at CERN (CalDet)
  • Small version of Near and Far detectors
  • Exposed to m, p, e, p beams 0.5-10 GeV
  • Hadronic & EM energy response
  • Tune the MC

Jeff Hartnell, IoP Particle Physics 2004

neutrino energy reconstruction
Neutrino Energy Reconstruction
  • Need to accurately determine original neutrino energy to see “the dip”.

En = EHad + Em(Visible)

  • Em= f(Range) &

f(B-Curvature)

  • EHad= f(Energy Dep.)

hadrons

μ

5 m

hadrons

1.5 m

Jeff Hartnell, IoP Particle Physics 2004

calibrating the calorimeter
Problems:

Scintillator output varies by up to 20% from strip to strip.

Light output depends on particle type and particle energy.

Calibrating the Calorimeter

Solutions:

Normalise using cosmic muons.

Measure response with

Calibration Detector in MEU/GeV.

(MEU=Muon Energy Unit)

Jeff Hartnell, IoP Particle Physics 2004

why stopping muons
Why Stopping Muons?
  • Need a calibration source of known energy - a “standard candle”.
  • Don’t have a “PS” accelerator ½ mile underground to provide beams of particles
  • The energy spectrum of cosmic muons (and hence energy deposition) is different for Near and Far detectors and not known accurately enough.
  • Working backwards from the end of a stopping muon track you know its energy – Use to define a Muon Energy Unit (MEU).
  • Stopping muons are the same at all 3 detectors!

Jeff Hartnell, IoP Particle Physics 2004

stopping beam muons in caldet at 1 8 gev c

Relativistic rise in

ionisation ~10%

Muons stop

here

Stopping Beam Muons in CalDet (at 1.8 GeV/c)

Beam Direction

Corrected ADCs

Plane

Jeff Hartnell, IoP Particle Physics 2004

track window method

Window

Track Window Method
  • Want a method that is inherently robust and not sensitive to reconstruction problems.
  • Sum up the energy deposition in a window.
  • Define a Muon Energy Unit (MEU) to be the average energy deposited in the window by a perpendicular muon in one detector plane.

Jeff Hartnell, IoP Particle Physics 2004

conclusion
Conclusion
  • The main physics measurement requires accurate reconstruction of the neutrino energy to 5%.
  • Explained how MINOS has 3 detectors in very different environments. Need to set the absolute energy scale to be the same for each detector.
  • No beam source of GeV particles for calibration underground so use stopping cosmic muons.
  • Take a window on the stopping muon track to measure the detector response.
  • Should enable us to meet our 2% relative calibration target and hence accurately measure Dm2.

Jeff Hartnell, IoP Particle Physics 2004