1. High Energy Neutrino Detectors Deborah Harris Fermilab Nufact’05 Summer Institute June 14-15, 2005

2. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 2 Outline of this Lecture Introduction –What are the goals? –Particle Interactions in Matter Detectors –Fully Active Liquid Argon Time Projection Cerenkov (covered in later talk) –Sampling Detectors Overview: Absorber and Readout Steel/Lead Emulsion Scintillator/Absorber Steel-Scintillator

3. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 3 For Each Detector Underlying principle Example from real life What do events look like? –Quasi-elastic Charged Current –Inelastic Charged Current – Neutral Currents Backgrounds Neutrino Energy Reconstruction What else do we want to know? All detector questions are far from answered!

4. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 4 Detector Goals Identify flavor of neutrino –Need charged current events! –Lepton Identification (e,  ) Measure neutrino energy –Charged Current Quasi-elastic Events You will derive this later today, but all you need is the lepton angle and energy Corrections due to –P,n motion in nucleus –U,d motion in nucleon –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..

5. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 5 Making a Neutrino Beam Conventional Beam Beta Beam Neutrino Factory For each of these beams, flux (Φ) is related to boost of parent particle (  )

6. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 6 Goals vs Beams  Conventional Beams ( , % e ) –Identify muon in final state –Identify electron in final state, subtract backgrounds –Energy regime: 0.4GeV to 17GeV   beams (all e ) –Idenify muon or electron in final state –Energy regime: <1GeV for now  Neutrino Factories ( , e ) –Identify lepton in final state –Measure Charge of that lepton! Charge of outgoing lepton determines flavor of initial lepton –Energy regime: 5 to 50GeV ’s

7. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 7 Next Step in this field: appearance!  13 determines –If we’ll ever determine the mass hierarchy –The size of CP violation How do backgrounds enter? –Conventional beams:  → e Already some e in the beam Detector-related backgrounds: –Neutrino Factories: No beam-related backgrounds for e →  Detector-related backgrounds:

8. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 8 Why do detector efficiencies and background rejection levels matter? Which detector does better (assume 1%  - e oscillation probability) –5 kton of 50% efficient for e 0.25% acceptance for NC –15kton of 30% efficient for e 0.5% acceptance for NC events? Assume you have a convenional neutrino beamline which produces: 1000   CC events per kton (400NC events) 5 e CC events per kton Background: ( 5*.5 e + 400*.0025NC)x5=17.5 Signal: (1000*.01*.5)x5=25, S/sqrt(B+S)=3.8 Background: ( 5*.3 e + 400*.005NC)x15=52.5 Signal: (1000*.01*.3)x15=45, S/sqrt(B+S)=4.6

9. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 9 Now for a Factory… Assume you have a neutrino factory which produces: 500   CC events per kton (200NC) 1000 e 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 12  result instead of a 4  result, or being sensitive at 3  to a 10 times smaller probability! Note: as muon energy increases, you get more /kton for a  factory!

10. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 10 Particles passing through material ParticleCharacteristic Length Dependence ElectronsRadiation length (X o )Log(E) Hadrons Interaction length ( INT ) Log(E) MuonsdE/dxE TausDecays first  ct=  87  m MaterialX o (cm) INT (cm) dE/dx (MeV/ cm)  (g per cm 3 ) L.Argon1483.52.11.4 Water3783.62.01 Steel1.761711.47.87 Scintillator42~801.91 Lead0.561712.711.4

11. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 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  INT =83cm 3.6x3.9x19.1m 3 600 ton module (480fid)

12. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 12 View of the inner detector Half Module of ICARUS

13. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 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

14. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 14 Principle of Liquid Argon TPC Time Drift direction E drift High density Non-destructive readout Continuously sensitive Self-triggering Very good scintillator: T 0 dE/dx(mip) = 2.1 MeV/cm T=88K @ 1 bar W e ≈24 eV W  ≈20 eV Charge recombination (mip) @ E = 500 V/cm ≈ 40% Readout planes: Q Continuous waveform recording Low noise Q-amplifier

15. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 15 dE/dx in Materials Bethe-Block Equation x in units of g/cm 2 Energy Loss Only f(  ) Can be used for Particle ID in range of momentum

16. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 16 Bethe-Block in practice From a single event, see dE/dx versus momentum (range) ABAB BC K+ µ+ Run 939 Event 46 A B C D K+ µ+ e+

17. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 17 Examples of Liquid Argon Events Lots of information for every event… e -, 9.5 GeV, p T =0.47 GeV/c CNGS  interaction, E =19 GeV  -  e - + e +  _ e -, 15 GeV, p T =1.16 GeV/c Vertex: 1  0,2p,3n,2 ,1e - CNGS e interaction, E =17 GeV Courtesy André Rubbia  Primary  tag:  e  decay  Exclusive  tag:  decay  Primary Bkgd: Beam e

18. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 18  0 identification in Liquid Argon Preliminary MeV/cm cut 1 π 0 (MC) One photon converts to 2 electrons before showering, so dE/dx for photons is higher… Imaging provides ≈2  10-3 efficiency for single  0

19. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 19 Oustanding Issues 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? Liquid Argon Time Projection Chamber

20. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 20 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)

21. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 21 Sampling calorimeters High Z materials: –mean smaller showers, –more compact detector –Finer transverse segmentation needed Low Z materials: –more mass/X 0 (more mass per instrumented plane) –Coarser transverse segmentation –“big” events (harsh fiducial cuts for containment) MaterialX o (cm)l INT (cm)Sampling (X o X o (g/cm 2 ) L.Argon1483.5.2 (ICARUS)20 Water183.6.33 (NuMI OA)36 Steel1.76171.4 (MINOS)14 Scintillator42~80.33 (NO A) 40 Lead0.5617.2 (OPERA)6

22. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 22  detection (OPERA) Challenge: making a Fine-grained and massive detector to see kink when tau decays to something plus 

23. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 23 Lead-Emulsion Target Emulsion films (Fuji) mass production started in April ‘03 production rate ~8,000m 2 /month (206,336 brick  ~150,000m 2 ) Lead plates (Pb + 2.5% Sb) requirements: low radioactivity level, emulsion compatibility, constant and uniform thickness 6.7m Wall prototype 2 emulsion layers (44  m thick) glued onto a 200  m plastic base 52 x 64 bricks 12.5cm 10.2cm Pb 1 mm   8.3kg 10 X0’s BRICK: 57 emulsion foils + 56 interleaved Pb plates Total target mass : 1766 t

24. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 24 Particle ID in Emulsion pions protons Test exposure (KEK) : 1.2 GeV/c pions and protons, 29 plates 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. Plots courtesy M. DeSerio

25. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 25 One cannot live by Emulsion alone 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) Track segments found in 8 consecutive plates Connected tracks with >= 2 segments Passing- through tracks rejection Vertex reconstructin

26. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 26 Muon Spectrometer w/RPC B= 1.55 T base slabs coil 8.2 m M ~ 950t Drift tubes 12 Fe slabs (5cm thick) RPC’s 2 cm gaps  identification:  > 95% (TT)  p/p < 20%, p < 50 GeV/c p < 50 GeV/c  charge  charge Mis-id prob.  0.1  0.3%  0.1  0.3% 21 bakelite RPC’s (2.9x1.1m 2 ) / plane (~1,500m 2 / spectrometer) pickup strips, pitch: 3.5cm (horizontal), 2.6cm (vertical) Inner Tracker: 11 planes of RPC’s Precision tracker: 6 planes of drift tubes diameter 38mm, length 8m efficiency:  99% space resolution:  300µm RPC: gives digital information about track: has been suggested for use in several “huge mass steel detectors” (Monolith)

27. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 27  detection (OPERA) Detection Efficiency

28. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 28  backgrounds Cut on invariant mass of primary tracks

29. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 29  events expected (OPERA) Comparison: 4  events over 0.34 background at DONUT.27kton  m 2  m 2 ( x 10 -3 eV 2 ) Back- ground 1.9 2.4 3.0   µ  µ 2.23.65.6 0.23   e  e 2.74.3 6.70.23   h  h 2.43.8 5.90.32    3h 0.71.1 1.70.22 Total 8.012.8 19.91.0

30. 14-15 June 2005Deborah Harris High Energy Neutrino Detectors 30 Outstanding Issues If LSND signature is oscillations,  appearance will be much more important in the future For future neutrino factory experiments, could study e  →  For either of these topics, need to understand if/how magnetic field can be made… Any way to make this detector more massive? Emulsion Sampling