How to Build a Neutrino Oscillations Detector - Why MINOS is like it is!

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How to Build a Neutrino Oscillations
Detector-Why MINOS is like it is!

• Alfons Weber
• March 2005

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Neutrino Oscillations

• MINOS is a long baseline Neutrino Oscillation
  Experiment
• What do we want to measure?
• We want to see, how one type of Neutrino
  transforms itself into another.
• There is a characteristic pattern, if this is
  transformation is due to neutrino mass
  eigenstates
• Simplified two neutrino scenario

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How are Neutrinos produced?
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NuMI The Main Injector
Fermilab Main Injector 120 GeV protons
2.5 x 1013 protons/pulse 1.9 sec
rep rate (8 msec spill)
? 0.25 MW NuMI Beam Graphite
target Two magnetic horns 675 m.
vac. decay pipe hadron absorber
designed for 4 x 1013 ppp Beam Monitoring
muon detectors hadron detectors
Near Detector !
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NuMI Beam Layout
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Neutrino Production
120 GeV primary Main Injector beam Target readily
movable in beam direction 2-horn beam adjusts
for variable energy ranges 675 meter decay pipe
for p decay
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MINOS Physics Reach

• Intense nm beam from FNAL
• - initially 2.5 x 1020 p.o.t./year,
• (being commisioned now !!)

Nominal Beam Configurations
?µ CC Events/year (with no oscillations) Low
Medium High 1,600 4300 9250
Beam spectra M. Messier
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Neutrino Interactions

• Charge current
• electron
• muon
• tau
• Can measure neutrino energy
• Neutral Current
• electron
• muon
• tau

hadrons
? µ
µ
5 m
hadrons
? µ
? µ
1.5 m
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Oscillation Pattern
No Effect!
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MINOS Analysis

• Select ?µ charge current events and reconstruct
  neutrino energy
• Energy resolution
• Compare energy spectrum in near and far detector
• Measure ?m2 and sin22?
• Look for appearance of ?e
• beam NC contamination

range, B field
calorimetric
?m2
sin22?
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Where should the Experiment be?

• ?m2 0.002-0.003 eV2 (from SK)
• In oscillation Minimum L/E 400 - 800 km /
  GeV
• Larger distance ? shorter distance
• High energy ? low energy
• Flux 1/L2
• Cross section E
• Event size E

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The MINOS Experiment

• NuMI beam travels 735 km to Soudan (MN)
• Sagitta10 km
• 1 km wide at destination

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How many detectors?
Where?
Why?
W I C H T Y P E?
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Detector

• Design requirements
• High Mass
• High segmentation
• Affordable

Pick any 2!
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MINOS Detectors

• There are 3 MINOS Detectors
• Near Detector _at_ FNAL (ND)
• Far Detector _at_ Soudan (FD)
• Calibration Detector _at_ CERN (CalDet)
• Magnetised steel scintillator tracking
  calorimeter
• Alternating planes of steel and scintillator
  strips

12 ton
0.9 kton
5.4 kton
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Soudan Underground Laboratory

• former iron mine, now a state park,
• home of Soudan-1 2 , CDMS-II , and MINOS expts

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MINOS Construction Challenge

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MINOS Plane
2-m wide, 0.5-inch thick steel plates
Bottom steel plane layer
Scintillator plane Orientations alternate ?90o in
successive planes
Top steel plane layer
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Far Detector

• In old iron mine
• Was already there
• Soudan 1 2
• Right distance from FNAL

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MINOS Scintillator Module

• 4-8m scintillator modules
• 24-28 strips
• double sided readout
• multi anode PMTs (16/64)

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PMT

• Light is detected bymulti-anode PMTs
• 230x 64-pixel in ND
• 1500x 16-pixel in FD
• pixel to pixel variations

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FD Front End Electronics

• MINOS developed an ASIC chip for PMT readout
• 32 channels
• shaping
• amplification
• sample hold
• output driver to ADC
• Excellent product
• fast shaping 500 nsec
• noise lt 2 fC
• lineargt 20 pC
• 6 ASICs multiplexed onto 1 ADC

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Signal Amplification
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Output of Pre-amplifier
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Signal Digitisation
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DAQ System

• Trigger-less DAQ system
• ASIC close to PMT
• ADC in VME crate
• fast PVIC-bus to PC trigger farm
• search for hits correlated in space and time

• Timing System
• Absolute time from GPS(?tabs 200 nsec)
• optical distribute along large detector (?trel
  4 nsec)

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Near Detector Event
Low-energy track from fiducial region
MINOS Preliminary Etrack approx. 1.5 GeV
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Additional Near Detector Events
Medium energy track from near peak in
pseudo-medium beam
MINOS Preliminary Etrack approx. 3.1 GeV
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Additional Near Detector Events
One snarl (beam pulse) in near detector,
showing multiple events.
MINOS Preliminary