1. NuMI Off-Axis Experiment Alfons Weber University of Oxford & Rutherford Appleton Laboratory EPS2003, Aachen July 19, 2003

2. 19/7/20032 Content What is the physics? Why off-axis? The beam The site What experiment to build? Scintillator Resistive plate chambers (Liquid Argon) Sensitivity

3. 19/7/20033 What is the Physics? Precision Experiment to determine  m 23 sin 2 2  23 Look for sub-dominant oscillation mode sin 2  13 Needed: low background Low e beam contamination Few wrong energy neutrinos

4. 19/7/20034 Why Off-Axis  e (|U e3 2 | = 0.01) e background NC (visible energy), no rejection  spectrum NuMI beam can produce 1-3 GeV intense beams with well defined energy in a cone around the nominal beam direction

5. 19/7/20035 NuMI beam 120 GeV protons from FNAL main injector 3-15 GeV neutrinos 3.8x10 20 PoT / year 0.5 MW beam power Baselines 700-950 km Several sites with infrastructure Road Electricity Network Possible Sites Canada U.S. L. Superio r Soudan

6. 19/7/20036 Experimental Challenge Small signal huge # NC Surface detector No or light over- burden cosmic   induced n But: Duty factor 10 -5

7. 19/7/20037 Detector Challenge NC versus Electron CC separation Fine grain Low Z Build affordable & massive detector 50+ kton fiducial mass >400k readout channels Technologies: Solid scintillator (MegaMINOS, but not Mton) Liquid scintillator Glass RPCs (Liquid Argon TPC)

8. 19/7/20038 Alternating horizontal and vertical scintillator planes Passive material: wood Oriented Strand Board (density.6 -.7 g/cm 3 ) Sampling: 1/3 rad. length readout 15 m Scintillator modules 4 ft 48 ft 8 ft 8 in 9.4 tons 5300 = detector 6 = 1 plane 180 m 885 planes = detector Fiducial fraction (1 m cut at all edges) 80% Solid/Liquid Sintillator

9. 19/7/20039 Scintillator Length 15 m Looped fibre readout Scintillator Material Solid MINOS like co-extruded (3.8x1 cm 2 ) Liquid Bicron 517 L (3.8x2.9 cm 2 ) WLS Fiber Kuraray (0.7 mm ø) Photodetector APD PMT: M64 Length in cm Relative Light Yield MINOS WLS Fiber 680,000 channels ( 30 x MINOS) ( 2 x MINOS) Scintillator and WLS Fibre 400,000 m 2 ( 16 x MINOS)

10. 19/7/200310 Glass RPCs / LSTs Used successfully Belle: 4 years operation Virginia Tech: 5 years testing Wood/plastic absorber

11. 19/7/200311 Signal & BG Events typical signal eventBG event Fuzzy track = e - Clean track = muon2 tracks = π 0

12. 19/7/200312 Physics Reach (I) Phase I (2008-2014) 4x10 20 PoT / year 50 kton detector (fiducial) 1.5 years neutrinos 5 years anti-neutrinos Phase II (2014-2020) A factor of 25 more: PoT x detector mass 1.5 years neutrinos 5 years anti-neutrinos

13. 19/7/200313 Physics Reach (II) Some Math: need more than one experiment to determine oscillation parameters A. Cervera et al., Nuclear Physics B 579 (2000) 17 – 55, expansion to second order in P (   e ) = P 1 + P 2 + P 3 + P 4

14. 19/7/200314 Physics Reach (III) Measurement is oscillation probability Depends simultaneously on: Mass hierarchy CP phase Mixing angles Typical Errors

15. 19/7/200315 Summary The NuMI OA group is seriously trying to bring froward a credible & affordable proposal Combination of JPARC/SuperK and NuMI OA neutrino and anti-neutrino running might reveal neutrino mixing parameters Masses & hierarchy Angles CP phase For more information: http://www-off-axis.fnal.gov

16. 19/7/200316 Liquid Argon TPC  Excellent pattern recognition capabilities  High efficiency for electron identification  Excellent e/  0 rejection