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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



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