Neutrino Oscillation Detectors: a (Re?)View

1. Neutrino Oscillation Detectors:a (Re?)View • Where we are? • Where are we going? • How do we get there? More questions than answers Adam Para, Fermilab NuFact 02, Imperial College, London July 5 2002

2. Quark and Neutrinos Mixing (Kayser representation) Weak eigenstates are mixtures of mass(strong) eigenstates Weak eigenstates are mixtures of mass eigenstates Mixing pattern for quarks and leptons is very different. Curious…Very curious.. What is it telling us??

3. Completing the Neutrino Mixing Matrix Small, otherwise known as: Please, please, please.. Can we settle on one convention? sin22q13? How small is ‘small’? |S|<0.17 • If ‘small’ is not too small, then: • mass hierarchy • CP violating phase d First step: determine/improve limit on sin22q13

4. Roadmap I • Agreed (?): • nmne oscillation experiment • Conventional beams (they are super!) • NuMI (2005) • JHF (2007-8) • Sensitivity down to sin22q13~0.003 • we think it is worth ~300-400 M$ (50+50, 200+100) and 3000 man-years (physicist-years?) • ~ results by 2015 Major branch point: • positive outcome of MiniBoone experiment

5. Roadmap II (??) ne appearance observed Neutrino mass hierarchy CP violation NuMI OA, Phase II, new proton driver JHF Phase II $1.5B (0.5 + 1) Results by 2025 Major branch point: Dm212 very small ‘Cheap’ version of neutrino factories technically feasible Somebody builds a gigantic water Cherenkov/LA somewhere ne appearance not observed Improve sensitivity down to sin22q13~0.0003 NuMI OA, Phase II, new proton driver JHF Phase II $1.5B (0.5 + 1) one? Both??? Results by 2025 Major branch point: ‘Cheap’ version of neutrino factories technically feasible Somebody builds a gigantic water Cherenkov/LA somewhere Is it worth the money/effort? Are there more important issues?

6. Roadmap III(???) • Ultimate limit on sin22q13 , or • Precision determination of CP violation in leptonic sector • Lepton number violation, new physics • Precision measurements • Life sciences • Neutrino Factory • Near detectors, intermediate detector, far detector • $2-3 B • 2030

7. So, what about detectors? Detectors are not generic. Their design depends on: • Energy regime: • JHF – mostly quasi-elastics, 1p • NuMI – few pions, range out • NuFact – many pions, showers • Required performance: • Detect/identify ne interactions • Reject NC/p0 • Detect wrong sign muons • Detect electrons determine sign • Detect taus, determine sign JHF NUMI Nu Fact Super-beams Neutrio Factories

8. CC ne / NC interactions ~ 2 GeV > 5 GeV Sophisticated imaging calorimeter, or Give up/ focus on muons Fine grained, relatively simple tracking calorimeter ?

9. Beam-Detector Interactions • Optimizing beam can improve signal • Optimizing beam can reduce NC backgrounds • Optimizing beam can reduce intrinsic ne background • Easier experimental challenge, simpler detectors • # of events ~ proton intensity x detector mass • Split the money to maximize the product, rather than individual components

10. ne identification/background rejection: beam + detector issue n spectrum NC (visible energy), no rejection Spectrum mismatch: These neutrinos contribute to background, but no signal ne background ne (|Ue3|2 = 0.01) NuMI low energy beam NuMI off-axis beam These neutrinos contribute to background, but not to the signal

11. On the Importance of the Energy Resolution • First oscillation minimum: energy resolution/beam spectrum ~ 20% well matched to the width of the structure • Second maximum: 20% beam width broader than the oscillation minimum, need energy resolution <10%. Tails?? • First oscillation minimum: energy resolution/beam spectrum ~ 20% well matched to the width of the structure • Second maximum: 20% beam width broader than the oscillation minimum, need energy resolution <10%. Tails?? • cut around the expected signal region too improve signal/background ratio • High energy tails of the resolution function very important

12. JHF-Kamioka Neutrino Project (hep-ex/0106019) Plan to start in 2007 0.77MW 50 GeV PS 4MW 50 GeV PS Kamioka ~1GeV n beam ( conventional n beam) JAERI (Tokaimura) Detectors? • Phase-I ( Super-Kamiokande) • Phase-II (Hyper-K)

13. Water Cerenkov: good match for sub GeV region (JHF, SPL, BB) • ~1 GeV n beam for Quasi-elastic interactions • Simple event topology • High electron ID efficiency (~40%) • Good energy resolution (kinematics) m events En(reconstruct) s=80MeV En (True) En(reconstruct) – En (True) (MeV)

14. Super-Kamiokande 50,000 tonwater Cherenkov detector　(22.5 kton fiducial volume) ４１．４ｍ ４０ｍ

15. Hyper-Kamiokande (a far detector in the 2nd phase) Good for atm. n proton decay ~1,000 kt Candidate site in Kamioka

16. Water Cherenkovs in US? (hep-ex/0205040,0204037,hep-ph/0204208) Soudan Off-axis beams + 2 detectors Homestake WIPP 100km FNAL BNL

17. NuMI Beam: on and off-axis Det. 2 Det. 1 • Selection of sites, baselines, beam energies • Physcis/results driven experiment optimization

18. An example of a possible detector Low Z tracking calorimeter Issues: • absorber material (plastic? Water? Particle board?) • longitudinal sampling (DX0)? • What is the detector technology (RPC? Scintillator? Drift tubes?) • Transverse segmentation (e/p0) • Surface detector: cosmic ray background? time resolution? • . . . NuMI detector workshop: October/November Fermilab/Chicago

19. Constructing the detector ‘wall’ • Containment issue: need very large detector. Recall: K2K near detector – 1 kton mass, 25 tons fiducial, JHF proposal – 1 kton mass, 100 tons fiducial • Engineering/assembly/practical issues Solution: Containers ?

20. On the importance of being mobile:mammals vs dinosaurs? Sin22q13=0.05 Neutrino factory, somewhere? Here we come!

21. Detectors for a Neutrino Factory An easy case: wrong sign muons (nmne) magnetic detector Light yield as a function of a position  make module 2 times bigger (x and y) Fully loaded cost of a MINOS supermodule is $11M/2.8 kt 50 kton magnetized detector ~ $200 M Economy of scale ? MINOS Spermodule I

22. Full physics menu at the neutrino factory? Electron/tau ID in complex high energy events: Imaging detector ( Liquid Argon TPC) ne e- nmnm m- nt t- ne e+ ne nm m+ nt t+

23. Liquid Argon TPC • Excellent pattern recognition capabilities • High efficiency for electron identification • Excellent e/p0 rejection • t identification via kinematics a`la NOMAD • Lepton charge determination if in the magnetic field The only detector capable of fully exploiting the physics potential of the neutrino factory

24. Challenges of the Liquid Argon TPC • Cost effective implementation • Single large cryostat • Argon purity in large volumes • Long drift distance • Very high voltage • Safety, safety,safety • Data acquisition • A case of a dog, which did not bark (Conan Doyle) • 50 l prototype exposed to the WANF beam + NOMAD • 300 ton prototype exposed to cosmic rays in Pavia • No results (QE nm? ne? Angular distribution of CR muons? Uniformity of the detector? Long term stability? Other?) • Small LAr TPC in a neutrino beam at KEK or Fermilab ? : • Proof of principle as a reliable experimental technique • Rich source of physics information about low E neutrino interactions

25. Conclusions • We have a detector for low energy superbeams. Just need a beam. Water Cherenkovs likely to dominate this line of experiments for next 25 years • We have a medium energy superbeam. Just need a detector(s). Good ideas and a lot of engineering necessary to exploit the physics reach. Room for new developments. • We have minimal solution for a detector for the neutrino factory. We will build it in due time. • We have a 20 years old and still promising new technology. This is a major challenge. Need more effort here. • We are living in interesting times. Let’s go and look for ne appearance!

26. 11 Greatest Unanswered Questions of Physics • What is dark matter ? • What is dark energy ? • How were the elements from iron to uranium made? • Do neutrinos have mass ? • … • Are protons unstable ? • What is gravity ? • Are there additional dimensions ? • How did the Universe begin ? Discover February 2002