1. Sampling Detectors for e Detection and Identification Adam Para, Fermilab NuFact02 Imperial College Interest de jour: what is sin 2 2  13  oscillations   -> e ‘superbeams’ ‘Current’ generation of experiments How can we do better Sampling detectors for e detection

2. Different baselines: where the oscillation peaks are ? L(km)/n123 300 0.73 GeV 0.24 GeV 0.15 GeV 750 1.82 GeV 0.60 GeV 0.36 GeV 1500 3.64 GeV 1.21 GeV 0.73 GeV E < 1 GeV (KEK/JHF to SuperK, CERN to Frejus 0.3 < E < 3 GeV (NuMI) 0.5< E < 6 GeV (CERN to Taranto, BNL to ?) Flux/rates drop

3. Neutrino Cross Sections N+lepton N+l +  Many particles

4. Det. 2 What will MINOS do? Two functionally identical neutrino detectors Det. 1 "

5. e Interactions in MINOS? NC, E obs = 3 GeV e CC, E tot = 3 GeV NC interactions: Energy distributed over ‘large’ volume Detector Granularity: Longitudinal: 1.5X 0 Transverse: ~R M e CC interactions (low y) : Electromagnetic shower: Short Narrow Most of the energy in a narrow cluster energy

6. Needle in a Haystack ? NC Background e (|Ue3|2 = 0.001) e background NC (visible energy), no rejection spectrum Spectrum mismatch: These neutrinos contribute to background, but no signal

7. MINOS Limits on  to e Oscillations Sample of e candidates defined using topological cuts 10 kton-yr exposure,  m 2 =0.003 eV 2, |U e3 | 2 =0.01: Signal (  = 25%) - 8.5 ev e background - 5.6 ev Other (NC,CC,  ) – 34.1 ev M. Diwan,M. Mesier, B. Viren, L. Wai, NuMI-L-714 90% CL: | U e3 | 2 < 0.01 Limit comparable to a far superior detector (ICARUS) in CNGS beam

8. Receipe for a Better Experiment More neutrinos in a signal region Less background Better detector (improved efficiency, improved rejection against background) Bigger detector Lucky coincidences : distance to Soudan = 735 km,  m 2 =0.025-0.035 eV 2 Below the tau threshold! (BR(  ->e)=17%)

9. Two body decay kinematics ‘On axis’: E =0.43E  At this angle, 15 mrad, energy of produced neutrinos is 1.5-2 GeV for all pion energies  very intense, narrow band beam

10. Off-axis ‘magic’ ( D.Beavis at al. BNL Proposal E-889) 1-3 GeV intense beams with well defined energy in a cone around the nominal beam direction

11. NC/ e /  0 detectors

12. CHARM II (  e scattering) Challenges: Identify electrons Small cross section, large background from NC interactions Solution: Low Z, fine grained calorimeter

13. Detector(s) Challenge Surface (or light overburden)  High rate of cosmic  ’s  Cosmic-induced neutrons But:  Duty cycle 0.5x10 -5  Known direction  Observed energy > 1 GeV Principal focus: electron neutrinos identification Good sampling (in terms of radiation/Moliere length) Large mass: maximize mass/radiation length cheap

14. A possible detector: an example Cheap low z absorber: recycled plastic pellets Cheapest detector: glass RPC (?)

15. Constructing the detector ‘wall’ Containment issue: need very large detector Engineering/assembly/practical issues

16. On the Importance of the Energy Resolution M. Messier, Harvard U. Cut around the expected signal region too improve signal/background ratio

17. Energy resolution vis-à-vis oscillation pattern 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??

18. Energy Resolution of Digital Sampling Calorimeter Digital sampling calorimeter: 1/3 X0 longitudinal 3 cm transverse Energy = Cx(# of hits) DE ~ 15% @ 2 GeV DE ~ 10% 4-10 GeV ~15% non-linearity @ 8 GeV, no significant non- gaussian tails

19. Improve energy resolution? Total Absorption Calorimeter: HPWF Energy resolution limited by fluctuations of the undetected energy: nuclear binding energy, neutrinos and not by sampling fluctuations ‘Crude’ sampling calorimeter (CITFR), 10 cm steel, better energy resolution than total absorption one (HPWF)

20. Neutrino energy, Quasi-elastics ? E (reconstruct) – E (True) (MeV)  =80MeV E (reconstruct)  events  + n →  + p  p ( E , p  )

21. ~ 2 GeV: CC e / NC interactions

22. ~ 2 GeV:  CC interaction

23. ~ 7 GeV: CC e / NC interactions

24. CC e vs NC events: example Electron candidate: Long track ‘showering’ I.e. multiple hits in a road around the track Large fraction of the event energy ‘Small’ angle w.r.t. beam NC background sample reduced to 0.3% of the final electron neutrino sample (for 100% oscillation probability) 35% efficiency for detection/identification of electron neutrinos

25. Detector questions/issues What is the optimal absorber material (mostly an engineering/cost question, if  X 0 kept constant) What longitudinal sampling (  X 0 )? What is the desired density of the detector? (containment/engineering/transverse segmentation) Containment issues: fiducial volume vs total volume, engineering issues: what is the practical detector size? What is the detector technology (engineering/cost issue if transverse segmentation kept constant) What is the optimal transverse segmentation (e/p0, saturation,…) Can a detector cope with cosmic ray background? What is the necessary timing resolution?