1. Chris Smith California Institute of Technology EPS Conference 2003
The MINOS Detectors
Chris Smith
California Institute of Technology
EPS Conference 2003
Outline
The MINOS Experiment
Detector Technology
Far, Near and Calibration Detector
Detector Performance
Summary

2. The MINOS Experiment
Two Detector, long baseline, neutrino oscillation experiment:
NuMI beam (Neutrinos at the Main Injector)
Near Detector - on site at Fermilab
Far Detector – 730km away in Soudan mine, Minnesota
Calibration Detector – in a series of test-beams at CERN
Oscillations lead to differences in Near-Far event rates, energy spectra
Confirm Super-K result
Measure parameters to 10%
Near
Far
Chris Smith , Caltech

3. Detector Technology Iron/Scintillator tracking calorimeters
4.1 x 1cm scintillator strips, up to 8m long
Extruded polystyrene (co-extruded TiO2 coating)
PPO (1%), POPOP (0.03%) fluors
Readout via wavelength shifting fibres
Kuraray 1.2mm fibre (Y-11 fluor, 175 ppm)
Hamamatsu Multi-anode PMTs
Alternate planes rotated by  90o for 3D hits
Near and Far detectors magnetised
Chris Smith , Caltech

4. Far, Near and Calibration Detectoru v
Detectors are designed to be as similar as possible
Far: Large octagon, 5400 tons
Near: Squashed octagon, 980 tons
Calibration: Small section, 12 tons
Chris Smith , Caltech

5. Near Detector - FNAL 241 planes in 4 sections:
Veto
Target
Hadron Shower
Muon Spectrometer
Planes already constructed at FNAL
Beneficial occupancy in cavern from Dec 2003
Installation ~ 12 months
Chris Smith , Caltech

6. Far Detector – Soudan 2 supermodules, 484 planes
Plane installation completed June
2nd Coil installed July
Cosmic ray veto shield
Unmanned running expected August
Already taking CR and atmos n data
Chris Smith , Caltech

7. Calibration Strategy
MINOS designed for 2% relative (detector-detector) and 5% absolute energy calibration
Light Injection System
Electronics/PMT non-linearity
PMT gain shift
Cosmic ray muons
Strip-to-strip normalisation
Calibration Detector (CalDet)
Characterise muon, electron and hadron responses
Understand event topologies
Test calibration procedures
1 month running at FarDet  1 hour at CalDet
Chris Smith , Caltech

8. CalDet – CERN 1x1m cut-out section of larger MINOS detectors
60 planes x 24 strips for (x,y,z)
Double-ended read-out
Not magnetised
T11 T7
3.6 GeV/c
10 GeV/c
x 60
(3.7 m) 1m
24 strips
Scintillator
Steel
5.9 cm
CalDet exposed to T7 and T11 beams at CERN PS in summer 2001, 2002
Provides e, m, p, p from 0.2 – 10 GeV
Chris Smith , Caltech

9. Event Topologies at CalDet
Particle ID using TOF and Cerenkov detectors.
2 GeV topologies (single view):
(Without Single PEs)
Electron
Pion
Muon
Proton
Strip
Plane
Chris Smith , Caltech

10. Particle Response and Resolution
Preliminary results from CalDet agree well with predictions
Response
Resolution
Hadrons
47 MIPs/GeV
55%/E
Electrons
60 MIPs/GeV
22%/E
MC expectation
Chris Smith , Caltech

11. Timing Resolution at the Far Detector
Time Residuals for CR Muons
Resolution determined by decay time of Y-11 fluor in WLS fibre ~8 ns
Resolution measurement using down-going muons at Far Detector ~2.6 ns/plane
Expect ~2.5 ns based on photoelectron statistics for muons
Direction of muons can be determined with ~10 planes for contained vertex events
To distinguish up and down through-going muons need ~20 planes
 ~ 2.6 ns
Time (ns)
Chris Smith , Caltech

12. Light Output Factors affecting light at phototube include
Map of scintillator strip (Far Detector)
Light Output
Factors affecting light at phototube include
Scintillator light output
Path-length in strip
Attenuation in WLS fibres
Connector efficiency
Apply corrections to infer response for perpendicular plane crossing (through 1cm scintillator)
Observe ~8-10 PEs/strip for cosmic ray muons at surface
Fit to a muon energy spectrum
Chris Smith , Caltech

13. Candidate Neutrino Events at FarDet
Contained vertex atmospheric neutrino event?
NO!
CR muons entering between planes mimic atmospheric n events
MINOS uses a double layer of scintillator to give  95% efficiency and to prevent gaps
Strip vs Plane
U view
V view
Y vs X y x z
Chris Smith , Caltech

14. Candidate Neutrino Events at FarDet
Up-going muons produced by n interactions in Earth’s crust y
Y vs X
Y vs Z
Strip vs Plane
Time vs Y
Time vs Z x z
Example event: m+ p = 5.4GeV/c
Expect ~450 up-going events in 5 year exposure of MINOS
B field allows m charge to be measured up to ~100 GeV
Chris Smith , Caltech

15. Summary Far Detector construction completed on schedule
Very successful installation
CR and atmospheric neutrino data regularly being taken
Data analysis underway
Near Detector preparations underway
Planes assembled on surface ready for installation
Beneficial occupancy in cavern from December ‘03
CalDet data-taking and analysis has produced preliminary results
Good agreement with predictions
Test-beam run this summer will be used to compare Near and Far detector electronics
MINOS is in good shape for NuMI beam in Dec ‘04!
Chris Smith , Caltech