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High Energy Neutrino Detectors
Deborah Harris
Fermilab
Nufact’05 Summer Institute
June 14-15, 2005
14-15 June 2005 Deborah 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
14-15 June 2005 Deborah 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!
14-15 June 2005 Deborah 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..
E
LmP
4sin2sin
222
pln
nlp
lXN
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 5
Making a Neutrino Beam
• Conventional Beam
• Beta Beam
• Neutrino Factory
2For each of these beams,
flux (Φ) is related to boost of parent particle ()
14-15 June 2005 Deborah 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
14-15 June 2005 Deborah 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:
14-15 June 2005 Deborah 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
14-15 June 2005 Deborah 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!
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 10
Particles passing through material
Particle Characteristic Length Dependence
Electrons Radiation length (Xo) Log(E)
Hadrons Interaction length (INT) Log(E)
Muons dE/dx E
Taus Decays first ct=87m
Material Xo
(cm)
INT(cm) dE/dx
(MeV/cm)
(g per
cm3)
L.Argon 14 83.5 2.1 1.4
Water 37 83.6 2.0 1
Steel 1.76 17 11.4 7.87
Scintillator 42 ~80 1.9 1
Lead 0.56 17 12.7 11.4
14-15 June 2005 Deborah 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=14cmINT =83cm
• 3.6x3.9x19.1m3 600 ton module (480fid)
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 12
View of the inner detector
Half Module of ICARUS
14-15 June 2005 Deborah 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 R
econstructed Event
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 14
Principle of Liquid Argon TPC
Time
Drift direction
Edrift
•High density
•Non-destructive readout
•Continuously sensitive
•Self-triggering
•Very good scintillator: T0
dE/dx(mip) = 2.1 MeV/cmT=88K @ 1 barWe≈24 eVW≈20 eVCharge recombination (mip)@ E = 500 V/cm ≈ 40%
Readout planes: Q
Continuous waveform recording
Low noise Q-amplifier
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 15
dE/dx in Materials
• Bethe-Block Equation • x in units of g/cm2
• Energy Loss Only f()• Can be used for Particle ID in
range of momentum
2
2ln
2
11 22
max222
22
I
Tcm
A
Zz
dx
dE e
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 16
Bethe-Block in practice
• From a single event, see dE/dx versus momentum (range)
AB
BC
K+
µ+
Run 939 Event 46
A
B
C
D
K+
µ+
e+
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 17
Examples of Liquid Argon Events
• Lots of information for every event…
e-, 9.5 GeV, pT=0.47 GeV/c
CNGS interaction, E=19 GeV
- e- + e + _
e-, 15 GeV, pT=1.16 GeV/c
Vertex: 10,2p,3n,2 ,1e-
CNGS e interaction, E=17 GeV
CourtesyAndré Rubbia
Primary tag:edecayExclusive tag:decayPrimary Bkgd: Beam e
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 18
0 identification in Liquid Argon
Preliminary
<dE/dx> MeV/cm
cut
1 π0 (MC)
One photon converts to 2 electrons before showering, so dE/dx for photons is higher…
Imaging provides ≈210-3 efficiency for single 0
14-15 June 2005 Deborah 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
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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)
N
X
electronE
electronE
NhadronE
hadronE
samplesNNE
E
INT
0
)(
)(
)(
)(
,1
14-15 June 2005 Deborah 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/X0 (more mass per instrumented plane)– Coarser transverse segmentation– “big” events (harsh fiducial cuts for containment)
Material Xo (cm) lINT(cm) Sampling (Xo Xo (g/cm2)
L.Argon 14 83.5 .2 (ICARUS) 20
Water 1 83.6 .33 (NuMI OA) 36
Steel 1.76 17 1.4 (MINOS) 14
Scintillator 42 ~80 .33 (NOA) 40
Lead 0.56 17 .2 (OPERA) 6
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detection (OPERA)
• Challenge: making a Fine-grained and massive detector to see kink when tau decays to something plus
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 23
Lead-Emulsion Target
Emulsion films (Fuji)Emulsion films (Fuji)mass production started in April ‘03
production rate ~8,000m2/month(206,336 brick ~150,000m2)
Lead plates Lead plates (Pb + 2.5% Sb)(Pb + 2.5% Sb)requirements:
low radioactivity level,emulsion compatibility,
constant and uniform thickness
6.7m
Wall prototypeWall prototype
2 emulsion layers (44 m thick)glued onto a
200 m plastic base
52 x 64 bricks52 x 64 bricks
12.5cm
10.2cmPb
1 mm
8.3kg
10 X0’s
BRICK: 57 emulsion foils +56 interleaved Pb plates
Total target mass : 1766 t
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 24
Particle ID in Emulsion
pionsprotons
Test exposure (KEK) : 1.2 GeV/c pions and protons, 29 plates
Grain density in emulsion is Grain density in emulsion is proportional to dE/dxproportional to dE/dx
By measuring grain By measuring grain density density
as a function of as a function of the distance from the distance from
the stopping pointthe stopping point,,particle identification particle identification can be performed can be performed. .
Plo
ts c
ourt
esy
M. D
eSer
io
14-15 June 2005 Deborah 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
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 26
Muon Spectrometer w/RPC
B=
1.5
5 T
base
slabs
coil
8.2
m
M ~ 950t
Drift tubes
12 Fe slabs(5cm thick)
RPC’s
2 cm gaps
identification: identification: > 95% (TT)> 95% (TT)
p/p < 20% ,p/p < 20% , p < 50 GeV/cp < 50 GeV/c
charge charge Mis-id prob.Mis-id prob.
0.1 0.1 0.3% 0.3%
21 bakelite RPC’s (2.9x1.1m2) / plane (~1,500m2 / spectrometer)
pickup strips, pitch: 3.5cm (horizontal), 2.6cm (vertical)
Inner Tracker: Inner Tracker: 11 planes of RPC’s11 planes of RPC’s
Precision tracker: Precision tracker: 6 planes of drift tubes6 planes of drift tubes
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)
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 27
detection (OPERA)
• Detection Efficiency
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 28
backgrounds
• Cut on invariant mass of primary tracks
14-15 June 2005 Deborah Harris High Energy Neutrino Detectors 29
events expected (OPERA)
Comparison: 4 events
over 0.34 background
atDONUT .27kton
mm22 ( x 10-3 eV2)Back-
ground 1.9 2.4 3.0
µ 2.2 3.6 5.6 0.23
e 2.7 4.3 6.7 0.23
h 2.4 3.8 5.9 0.32
3h 0.7 1.1 1.7 0.22
Total 8.0 12.8 19.9 1.0
14-15 June 2005 Deborah 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