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Sampling Detectors for n e Detection and Identification

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

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Sampling Detectors for n e Detection and Identification

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  1. Sampling Detectors for ne Detection and Identification • Interest de jour: what is sin22q13 • oscillations nm -> ne • ‘superbeams’ Adam Para, Fermilab NuFact02 Imperial College • ‘Current’ generation of experiments • How can we do better • Sampling detectors for ne detection

  2. Different baselines: where the oscillation peaks are ? En < 1 GeV (KEK/JHF to SuperK, CERN to Frejus 0.3 < En < 3 GeV (NuMI) 0.5< En < 6 GeV (CERN to Taranto, BNL to ?) Flux/rates drop

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

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

  5. ne Interactions in MINOS? ne CC, Etot = 3 GeV NC, Eobs = 3 GeV NC interactions: • Energy distributed over ‘large’ volume • neCC interactions (low y) : • Electromagnetic shower: • Short • Narrow • Most of the energy in a narrow cluster • Detector Granularity: • Longitudinal: 1.5X0 • Transverse: ~RM energy

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

  7. MINOS Limits on nm to neOscillations 10 kton-yr exposure, Dm2=0.003 eV2, |Ue3|2=0.01: Signal (e = 25%) - 8.5 ev ne background - 5.6 ev Other (NC,CC,nt) – 34.1 ev M. Diwan,M. Mesier, B. Viren, L. Wai, NuMI-L-714 90% CL: | Ue3|2< 0.01 Limit comparable to a far superior detector (ICARUS) in CNGS beam Sample ofnecandidates defined using topological cuts

  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, Dm2=0.025-0.035 eV2 • Below the tau threshold! (BR(t->e)=17%)

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

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

  11. NC/ ne /p0 detectors

  12. CHARM II (nme 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 m’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 ? m nm + n → m + p (Em, pm) n p m events En(reconstruct) s=80MeV En(reconstruct) – En (True) (MeV)

  21. ~ 2 GeV: CC ne / NC interactions

  22. ~ 2 GeV: nm CC interaction

  23. ~ 7 GeV: CC ne / NC interactions

  24. CC ne 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 DX0 kept constant) • What longitudinal sampling (DX0)? • 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?

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