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

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??

Completing the Neutrino Mixing Matrix How small is ‘small’? Small, otherwise known as: If ‘small’ is not too small, then: mass hierarchy CP violating phase  |S|<0.17 First step: determine/improve limit on sin 2 2  13 Please, please, please.. Can we settle on one convention? sin 2 2  13 ?

Roadmap I Agreed (?):    e oscillation experiment  Conventional beams (they are super!) NuMI (2005) JHF (2007-8)  Sensitivity down to sin 2 2  13 ~0.003  we think it is worth ~ M$ (50+50, ) and 3000 man-years (physicist-years?)  ~ results by 2015 Major branch point:  positive outcome of MiniBoone experiment

Roadmap II (??) e appearance observed  Neutrino mass hierarchy  CP violation NuMI OA, Phase II, new proton driver JHF Phase II $1.5B ( ) Results by 2025 Major branch point:  m 2 12 very small ‘Cheap’ version of neutrino factories technically feasible Somebody builds a gigantic water Cherenkov/LA somewhere e appearance not observed  Improve sensitivity down to sin 2 2  13 ~ NuMI OA, Phase II, new proton driver JHF Phase II $1.5B ( ) 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?

Roadmap III(???)  Ultimate limit on sin 2 2  13, 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

So, what about detectors? Detectors are not generic. Their design depends on: Energy regime: JHF – mostly quasi-elastics, 1  NuMI – few pions, range out NuFact – many pions, showers Required performance: Detect/identify e interactions Reject NC/  0 Detect wrong sign muons Detect electrons determine sign Detect taus, determine sign JHFNUMINu Fact Super- beams Neutrio Factories

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

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

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

On the Importance of the Energy Resolution cut around the expected signal region too improve signal/background ratio High energy tails of the resolution function very important First oscillatio n minimum: energy resolutio n/beam spectrum ~ 20% well matched to the width of the structur e Second maximum : 20% beam width broader than the oscillatio n minimum, need energy resolutio n <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??

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

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

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

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

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

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

An example of a possible detector Low Z tracking calorimeter Issues: absorber material (plastic? Water? Particle board?) longitudinal sampling (  X 0 )? What is the detector technology (RPC? Scintillator? Drift tubes?) Transverse segmentation (e/  0 ) Surface detector: cosmic ray background? time resolution?... NuMI detector workshop: October/November Fermilab/Chicago

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 ?

On the importance of being mobile: mammals vs dinosaurs? Neutrino factory, somewhere? Here we come! Sin 2 2  13 =0.05

Detectors for a Neutrino Factory An easy case: wrong sign muons    e ) 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

e  e -       -     - e  e + e     +      + Full physics menu at the neutrino factory? Electron/tau ID in complex high energy events: Imaging detector ( Liquid Argon TPC)

Liquid Argon TPC  Excellent pattern recognition capabilities  High efficiency for electron identification  Excellent e/  0 rejection   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

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  ? e ? 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

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 e appearance!

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