1. How to Build a Neutrino Oscillations Detector - Why MINOS is like it is! Alfons Weber March 2005

2. March 2005 A. WeberMINOS Experiment2 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:

3. March 2005 A. WeberMINOS Experiment3

4. March 2005 A. WeberMINOS Experiment4 NuMI & The Main Injector Fermilab Main Injector: 120 GeV protons 2.5 x 10 13 protons/pulse 1.9 sec rep rate (~8  sec spill)  0.25 MW NuMI Beam: Graphite target Two magnetic horns 675 m. vac. decay pipe hadron absorber designed for 4 x 10 13 ppp Beam Monitoring: muon detectors hadron detectors + Near Detector !

5. March 2005 A. WeberMINOS Experiment5 NuMI Beam Layout

6. March 2005 A. WeberMINOS Experiment6 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  decay Neutrino Production

7. March 2005 A. WeberMINOS Experiment7 MINOS Physics Reach ν µ CC Events/year (with no oscillations) Low Medium High 1,600 4300 9250 Nominal Beam Configurations  Intense  beam from FNAL - initially 2.5 x 10 20 p.o.t./year, (being commisioned now !!) Beam spectra: M. Messier

8. March 2005 A. WeberMINOS Experiment8 Charge current –electron –muon –tau –Can measure neutrino energy Neutral Current –electron –muon –tau μ ν μ hadrons 5 m ν μ hadrons ν μ 1.5 m Neutrino Interactions

9. March 2005 A. WeberMINOS Experiment9 Oscillation Pattern No Effect! measures  m 2 Smeared by resolution P ~ 1/2

10. March 2005 A. WeberMINOS Experiment10 MINOS Analysis Select ν μ charge current events and reconstruct neutrino energy  Energy resolution:  Compare energy spectrum in near and far detector  Measure Δm 2 and sin 2 2θ Look for appearance of ν e  beam & NC contamination range, B fieldcalorimetric Δm2Δm2 sin 2 2θ

11. March 2005 A. WeberMINOS Experiment11 Where should the Experiment be? Δm 2 = 0.002-0.003 eV 2 (from SK) In oscillation Minimum L/E = 400 - 800 km / GeV Larger distance  shorter distance High energy  low energy Flux ~ 1/L 2 Cross section ~ E Event size ~ E

12. March 2005 A. WeberMINOS Experiment12 NuMI beam travels 735 km to Soudan (MN) Sagitta:10 km 1 km wide at destination The MINOS Experiment

13. March 2005 A. WeberMINOS Experiment13

14. March 2005 A. WeberMINOS Experiment14 Detector Design requirements –High Mass –High segmentation –Affordable

15. March 2005 A. WeberMINOS Experiment15 MINOS Detectors There are 3 MINOS Detectors –Near Detector @ FNAL (ND) –Far Detector @ Soudan (FD) –Calibration Detector@ CERN (CalDet) Magnetised steel scintillator tracking calorimeter –Alternating planes of steel and scintillator strips 5.4 kton 12 ton 0.9 kton

16. March 2005 A. WeberMINOS Experiment16 Soudan Underground Laboratory former iron mine, now a state park, –home of: Soudan-1 & 2, CDMS-II, and MINOS expts

17. March 2005 A. WeberMINOS Experiment17 MINOS Construction Challenge

18. March 2005 A. WeberMINOS Experiment18 Bottom steel plane layer Top steel plane layer Scintillator plane Orientations alternate  90 o in successive planes 2-m wide, 0.5-inch thick steel plates MINOS Plane

19. March 2005 A. WeberMINOS Experiment19 Far Detector In old iron mine Was already there –Soudan 1 & 2 Right distance from FNAL

20. March 2005 A. WeberMINOS Experiment20 8 m Scintillator Module WLS Fibers Optical Connector Clear Fiber Ribbon Cable (2-6 m) Multiplex Box Multiplex Box PMTs Connection to electronics Connection to electronics MINOS Scintillator Module 4-8m scintillator modules 24-28 strips double sided readout multi anode PMTs (16/64)

21. March 2005 A. WeberMINOS Experiment21 PMT Light is detected by multi-anode PMTs –230x64-pixel in ND –1500x 16-pixel in FD pixel to pixel variations

22. March 2005 A. WeberMINOS Experiment22 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 < 2 fC –linear> 20 pC –6 ASICs multiplexed onto 1 ADC

23. March 2005 A. WeberMINOS Experiment23 Signal Amplification

24. March 2005 A. WeberMINOS Experiment24 Output of Pre-amplifier

25. March 2005 A. WeberMINOS Experiment25 Signal Digitisation

26. March 2005 A. WeberMINOS Experiment26 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 (  t abs = 200 nsec) –optical distribute along large detector (  t rel = 4 nsec)

27. March 2005 A. WeberMINOS Experiment27 Near Detector Event MINOS Preliminary E track approx. 1.5 GeV Low-energy track from fiducial region

28. March 2005 A. WeberMINOS Experiment28 Additional Near Detector Events MINOS Preliminary E track approx. 3.1 GeV Medium energy track from near peak in “pseudo-medium” beam

29. March 2005 A. WeberMINOS Experiment29 Additional Near Detector Events MINOS Preliminary One “snarl” (beam pulse) in near detector, showing multiple events.