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Accelerator Neutrino Oscillation Physics Lecture II

Join Deborah Harris for a detailed lecture on neutrino detector goals, interactions in matter, various detector types, and beam technologies. Learn about liquid argon TPC and the principles of neutrino energy reconstruction.

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Accelerator Neutrino Oscillation Physics Lecture II

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  1. Accelerator Neutrino Oscillation PhysicsLecture II Deborah Harris Fermilab SUSSP August 16, 2006

  2. Outline of this Lecture • Introduction • What are the detector goals? • Particle Interactions in Matter • Detectors • Fully Active • Liquid Argon Time Projection • Cerenkov (covered mostly in Atmospheric n Lectures) • Sampling Detectors • Overview: Absorber and Readout • Steel/Lead Emulsion • Scintillator/Absorber • Steel-Scintillator Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  3. For Each Detector • Underlying principle • Example from real life • What do n events look like? • Quasi-elastic Charged Current • Inelastic Charged Current • Neutral Currents • Backgrounds • Neutrino Energy Reconstruction • What else do we want to know? Warning: this lecture is a set of mini-lectures about different detectortechnologies… All detector questions are far from answered! Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  4. Detector Goals • Identify flavor of neutrino • Need charged current events! • Lepton Identification (e,m,t) • Measure neutrino energy • Charged Current Quasi-elastic Events • All you need is the lepton angle and energy • Corrections due to • p,n motion in nucleus • Everything Else • Need to measure energy of lepton and of X, where X is the hadronic shower, the extra pion(s) that is (are) made.. Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  5. Making a Neutrino Beam • Conventional Beam • Beta Beam • Neutrino Factory For each of these beams, n flux (Φ) is related to boost of parent particle (g) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  6. Goals vs n Beams • Conventional Beams (nm, %ne) • Identify muon in final state • Identify electron in final state, subtract backgrounds • Energy regime: 0.4GeV to 17GeV • b beams (all ne ) • Idenify muon or electron in final state • Energy regime: <1GeV for now • Neutrino Factories (nm, ne) • Identify lepton in final state • Measure Charge of that lepton! • Charge of outgoing lepton determines flavor of initial lepton • Energy regime: 5 to 50GeV n’s Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  7. Next Step in this field: appearance! • Q13 determines • If we’ll ever determine the mass hierarchy • The size of CP violation • How do backgrounds enter? • Conventional beams: nm→ ne • Already some ne in the beam • Detector-related backgrounds: Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  8. Why do detector efficiencies and background rejection levels matter? • Assume you have a convenional • neutrino beamline which produces: • 1000 nmCC events per kton (400NC events) • 5 ne CC events per kton • Which detector does better (assume 1% nm-ne oscillation probability) • 5 kton of • 50% efficient for ne • 0.25% acceptance for NC • 15kton of • 30% efficient for ne • 0.5% acceptance for NC events? Background: ( 5*.5 ne + 400*.0025NC)x5=17.5 Signal: (1000*.01*.5)x5=25, S/sqrt(B+S)=3.8 Background: ( 5*.3 ne + 400*.005NC)x15=52.5 Signal: (1000*.01*.3)x15=45, S/sqrt(B+S)=4.6 Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  9. Now for a n Factory… Assume you have a neutrino factory which produces: • 500 nmCC events per kton (200NC) • 1000 ne CC events per kton (400NC) Again, assuming 1% oscillation probability, but now the backgrounds are 10-4 (for all kinds of interactions), the signal efficiency is 50%, and again you have 15kton of detector (because it’s an easy detector to make)… Background: ( .0001*2100(CC+NC))x15=3 Signal: (1000*.01*.5)x15=150, S/sqrt(B+S)=12 Get a “figure of merit” of 12 instead of 3 or 4… which is like getting a 12s result instead of a 4s result, or being sensitive at 3s to a 10 times smaller probability! Note: as muon energy increases, you get more n/kton for a n factory! Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  10. Particles passing through material Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  11. Liquid Argon TPC (ICARUS) • Electronic Bubble chamber • Planes of wires (3mm pitch) widely separated (1.5m) 55K readout channels! • Very Pure Liquid Argon • Density: 1.4, Xo=14cm lINT =83cm • 3.6x3.9x19.1m3 600 ton module (480fid) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  12. Half Module of ICARUS View of the inner detector Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  13. Liquid Argon TPC • Because electrons can drift a long time (>1m!) in very pure liquid argon, this can be used to create an “electronic bubble chamber” Raw Data to Reconstructed Event Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  14. Principle of Liquid Argon TPC Readout planes: Q Time Edrift Drift direction Low noise Q-amplifier Continuous waveform recording • High density • Non-destructive readout • Continuously sensitive • Self-triggering • Very good scintillator: T0 dE/dx(mip) = 2.1 MeV/cm T=88K @ 1 bar We≈24 eV Wg≈20 eV Charge recombination (mip) @ E = 500 V/cm ≈ 40% Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  15. dE/dx in Materials • Bethe-Bloch Equation • x in units of g/cm2 • Energy Loss Only f(b) • Can be used for Particle ID in range of momentum Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  16. AB K+ µ+ BC Bethe-Bloch in practice K+ e+ B µ+ C A • From a single event, see dE/dx versus momentum (range) Question: how would This look different for a p→m event? Run 939 Event 46 Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  17. _ -  e- +  e +  Examples of Liquid Argon Events e-, 9.5 GeV, pT=0.47 GeV/c • Primary t tag: • edecay • Exclusive t tag: • r decay • Primary Bkgd: Beam ne • Lots of information for every event… CNGS  interaction, E=19 GeV e-,15 GeV, pT=1.16 GeV/c Courtesy André Rubbia Vertex: 10,2p,3n,2 ,1e- CNGS e interaction, E=17 GeV Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  18. p0 identification in Liquid Argon One photon converts to 2 electrons before showering, so dE/dx for photons is higher… Imaging provides ≈210-3 efficiency for single p0 1 π0 (MC) cut Preliminary <dE/dx> MeV/cm Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  19. Oustanding Issues Liquid Argon Time Projection Chamber • Do Simulations agree with data (known incoming particles) • Can a magnetic field be applied • Both could be answered in CERN test beam program • Is neutral current rejection that good? • How large can one module be made? • What is largest possible wire plane spacing? Several R&D Efforts world-wideworking to get >10kton detectors “on the mass shell” Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  20. Cerenkov Light As particles move faster than the speed of light in that medium, they emit a “shock wave” of light • For water, n(280-580nm)~1.33-6,so pthreshold≈1.3*mass • Threshold Angle: 42o • What is Threshold momentum for neutral pions? Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  21. Event Reconstruction in Cerenkov Detector • Vertex Point fit: time of flight should be as sharp as possible • Define set of in-time tubes • Use Hough Transform to find rings • Look for rings until you’re done • Particle ID • Corrections to Vertex • Energy Reconstruction • Decay Electron Finding Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  22. Particle ID Using Cerenkov Light Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  23. Super-Kamiokande detector 50,000 tonwater Cherenkov detector (22.5 kton fiducial volume) 1000m underground (2700 m.w.e.) 11,146 20-inch PMTs for inner detector 1,885 8-inch PMTs for outer detector

  24. Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  25. Single-Ring Energy Resolution • Tested in situ with LINAC at KEK Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  26. MiniBooNE detector: Cerenkov with Mineral Oil total volume: 800 tons (6 m radius) fiducial volume: 445 tons (5m radius) 1280 PMTs in detector at 5.5 m radius 10% photocathode coverage 240 PMTs in veto electron ring m ring Events courtesy G. Zeller Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  27. What about water Cerenkov at High (>1GeV) Energies??? Visible Energy = 2GeV: One Is e- One Is a p0 Courtesy Mark Messier: one is ne signal, one is p0 background Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  28. s(En) of Water Cerenkov vs En ne CC Reconstructed/True Energy nm CC NC Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  29. Oustanding Issues Cerenkov Detectors • What is largest vessel that can be made? (48mx58mx250m?) • What is highest energy regime that is possible, with better electronics,photo-detectors, etc? • Water Cerenkov clearly the cheapest per kton Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  30. e(Erecon) for Water Cerenkov Probability of ne CC Giving 1 e-like ring • Again, courtesy Mark Messier, for Fermilab to Homestake Study Reconstructed Energy (GeV) Probability of nm CC Giving 1 m-like ring Reconstructed Energy (GeV) Probability of n NC Giving 1 e-like ring Giving 1 m-like ring Reconstructed Energy (GeV) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  31. From Fully Active to Sampling • Advantages to Sampling: • Cheaper readout costs • Fewer readout channels • Denser material can be used • More N, more interactions • Could combine emulsion with readout • Can use magnetized material! • Disadvantages to Sampling • Loss of information • Particle ID is harder (except emulsion for taus in final state) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  32. Sampling calorimeters • High Z materials: • mean smaller showers, • more compact detector • Finer transverse segmentation needed • Low Z materials: • more mass/X0 (more mass per instrumented plane) • Coarser transverse segmentation • “big” events (harsh fiducial cuts for containment) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  33. nt detection (OPERA) • Challenge: making a Fine-grained and massive detector to see kink when tau decays to something plus nt Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  34. t Pb 1 mm 6.7m 10.2cm 12.5cm Emulsion films (Fuji) production rate ~8,000m2/month (206,336 brick  ~150,000m2) Lead plates (Pb + 2.5% Sb) requirements: low radioactivity level,emulsion compatibility, constant and uniform thickness Lead-Emulsion Target   2 emulsion layers (44 m thick) glued onto a 200 m plastic base 10 X0’s 8.3kg BRICK: 57 emulsion foils +56 interleaved Pb plates Wall prototype 52 x 64 bricks Total target mass : 1766 t Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  35. pions protons Particle ID in Emulsion Grain density in emulsion is proportional to dE/dx By measuring grain density as a function of the distance from the stopping point, particle identification can be performed. Test exposure (KEK) : 1.2 GeV/c pions and protons, 29 plates Plots courtesy M. DeSerio Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  36. One cannot live by Emulsion alone Passing-through tracks rejection • Need to know when interaction has happened in a brick • Electronic detectors can be used to point back to which brick has a vertex • Take the brick out and scan it (don’t forget to put a new brick in!) • Question: what can you use for the “electronic detectors” that point back to the brick? • (Hint: you’ve used up most of the money you have to buy emulsion, you need something cheap that can point well anyway) Connected tracks with >= 2 segments Track segments found in 8 consecutive plates Vertex reconstructin Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  37. coil M ~ 950t  charge Mis-id prob.  0.1  0.3% 12 Fe slabs (5cm thick) 8.2 m 2 cm gaps B= 1.55 T slabs RPC’s base Drift tubes Muon Spectrometer w/RPC p/p < 20% , p < 50 GeV/c • identification: •  > 95% (TT) Inner Tracker: 11 planes of RPC’s Precision tracker: 6 planes of drift tubes 21 bakelite RPC’s (2.9x1.1m2) / plane (~1,500m2 / spectrometer) pickup strips, pitch: 3.5cm (horizontal), 2.6cm (vertical) diameter 38mm, length 8m efficiency: 99% space resolution: 300µm RPC: gives digital information about track: has been suggestedfor use in several “huge mass steel detectors” (Monolith) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  38. nt detection (OPERA) • Detection Efficiency Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  39. nt backgrounds • Cut on invariant mass of primary tracks Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  40. nt events expected (OPERA) Comparison: 4 nt events over 0.34 background at DONUT .27kton Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  41. Outstanding Issues Emulsion Sampling • If LSND signature is oscillations, ntappearance will be much more important in the future • For future neutrino factory experiments, could study ne→ nt • For either of these topics, need to understand if/how magnetic field can be made… • Any way to make this detector more massive? Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  42. All Scintillator Detector 90 m • PVC extrusions • 17m tallx17m widex90m long • 3.87 cm transverse, 6 cm wide in beam direction (more light) • 17.5 m long vs. 48 ft (less light) • All Liquid Scintillator • 85% scintillator, 15% PVC • Previous design: inactive (particle board) plus active (scintillator) material, but was less efficient at rejecting backgrounds APD readout on TWO edges To Build: Glue Planes of Extrusions together Rotate them from horizontal to vertical Fill Extrusions with Liquid Scintillator Each box gets a WLS fiber loop (bent at far end) Instrument WLS fibers with Advanced PhotoDiodes Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  43. Scintillator Events (2GeV) nm + A -> p +m- ne+A→p p+p- e- n + A -> p + 3p± + p0 + n Particle ID: particularly “fuzzy” e’s long track, not fuzzy (m) gaps in tracks (p0 ?) large energy deposition (proton?) One unit is 4.9 cm (horizontal) 4.0 cm (vertical) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  44. Detector Volume • Scaling detector volume is notso trivial • At 30kt NOvA is about the same mass as BaBar, CDF, Dzero, CMS and ATLAS combined… • want monolithic, manufacturabile structures • seek scaling as surface rather than volume if possible Figure courtesy J.Cooper Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  45. Detector Volume, continued(courtesy K.McFarland) • Consider the Temple of the Olympian Zeus (right)… • 17m tall, just like NOvA! • a bit over ½ the length 17m • It took 700 years to complete • Fortunately construction technology has improved • Left: Stoa toy Attaloy 120m Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  46. Energy Resolution Energy Resolution • For ne CC events with a found electron track (about 85%), the energy resolution is 10% / sqrt(E) Measured – true energy divided by square root of true energy • This helps reduce the NC and nm CC backgrounds since they do not have the same narrow energy distribution of the oscillated ne’s (for the case of an Off Axis beam) Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  47. All Scintillator m / e separation electrons electrons muons muons • This is what it means to have a “fuzzy” track • Extra hits, extra pulse height • Clearly nm CC are separable from ne CC Average number of hits per plane Average pulse height per plane Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  48. Outstanding Issues Fine Grained Scintillator • How cheaply can this be made? • Do you need any passive absorber? • What is best choice for readout? • Must have confidence in ability to reduce Neutral Current Backgrounds Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  49. Steel/Scintillator Detector (MINOS) • 8m octagon steel & scintillator calorimeter • Sampling every 2.54 cm • 4cm wide strips of scintillator • 5.4 kton total mass • 486 planes of scintillator • 95,000 strips Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

  50.  e CC Event CC Event UZ VZ Simulated MINOS Events NC Event 3.5m 1.8m 2.3m Courtesy Chris Smith, FNAL Seminar • Long muon track + hadronic activity at vertex • Short showering event, often diffuse • Short event with typical EM shower profile En = Eshower + Pm Shower energy resolution: 55%/√E Muon momentum resolution: 6% range; 13% curvature Deborah Harris Accelerator Neutrino Oscillation Physics Lecture II

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