High Energy Neutrino Detectors

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High Energy Neutrino Detectors

• Deborah Harris
• Fermilab
• Nufact05 Summer Institute
• June 14-15, 2005

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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

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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?

All detector questions are far from answered!
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Detector Goals

• Identify flavor of neutrino
• Need charged current events!
• Lepton Identification (e,m,t)
• 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..

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Making a Neutrino Beam

• Conventional Beam
• Beta Beam
• Neutrino Factory

For each of these beams, n flux (F) is related to
boost of parent particle (g)
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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 lt1GeV 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 ns

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Next Step in this field appearance!

• Q13 determines
• If well 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
• Neutrino Factories
• No beam-related backgrounds for ne?nm
• Detector-related backgrounds

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Why do detector efficiencies and background
rejection levels matter?

• Assume you have a convenional
• neutrino beamline which produces
• 1000 nm CC 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)x517.5 Sign
al (1000.01.5)x525, S/sqrt(BS)3.8
Background ( 5.3 ne 400.005NC)x1552.5 Sign
al (1000.01.3)x1545, S/sqrt(BS)4.6
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Now for a n Factory

• Assume you have a neutrino factory
• which produces
• 500 nm CC 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 its
  an easy detector to make)

Background ( .00012100(CCNC))x153 Signal
(1000.01.5)x15150, S/sqrt(BS)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!
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Particles passing through material
Particle Characteristic Length Dependence
Electrons Radiation length (Xo) Log(E)
Hadrons Interaction length (lINT) Log(E)
Muons dE/dx E
Taus Decays first gctg87mm
Material Xo (cm) lINT(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
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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, Xo14cm lINT 83cm
• 3.6x3.9x19.1m3 600 ton module (480fid)

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Half Module of ICARUS
View of the inner detector
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Liquid Argon TPC
Raw Data to Reconstructed Event

• Because electrons can drift a long time (gt1m!) in
  very pure liquid argon, this can be used to
  create an electronic bubble chamber

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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 T88K _at_ 1 bar We24
eV Wg20 eV Charge recombination (mip) _at_ E 500
V/cm 40
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dE/dx in Materials

• Bethe-Block Equation
• x in units of g/cm2
• Energy Loss Only f(b)
• Can be used for Particle ID in range of momentum

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Bethe-Block in practice
D
B
e
K
C
µ
A
Run 939 Event 46
AB
K
µ
BC

• From a single event, see dE/dx versus momentum
  (range)

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Examples of Liquid Argon Events

• Lots of information for every event

• Primary t tag
• ?e decay
• Exclusive t tag
• ?r decay
• Primary Bkgd
• Beam ne

e-, 9.5 GeV, pT0.47 GeV/c
CNGS ?? interaction, E?19 GeV
e-, 15 GeV, pT1.16 GeV/c
Courtesy André Rubbia
Vertex 1?0,2p,3n,2 ?,1e-
CNGS ?e interaction, E?17 GeV
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p0 identification in Liquid Argon
1 p0 (MC)

• One photon converts to 2 electrons before
  showering, so dE/dx for photons is higher
• Imaging provides 2?10-3 efficiency for single p0

cut
Preliminary
ltdE/dxgt MeV/cm
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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?

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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)

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Sampling calorimeters
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 (NOnA) 40
Lead 0.56 17 .2 (OPERA) 6

• 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)

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nt detection (OPERA)

• Challenge making a Fine-grained and massive
  detector to see kink when tau decays to something
  plus nt

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Lead-Emulsion Target
?
??
2 emulsion layers (44 ?m thick) glued onto a
200 ?m plastic base
10 X0s
8.3kg
BRICK 57 emulsion foils 56 interleaved Pb
plates
Wall prototype
52 x 64 bricks
Total target mass 1766 t
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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
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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 (dont forget to
  put a new brick in!)
• Question what can you use for the electronic
  detectors that point back to the brick?
• (Hint youve used up most of the money you have
  to buy emulsion, you need something cheap that
  can point well anyway)

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Muon Spectrometer w/RPC
?p/p lt 20 , p lt 50 GeV/c

• identification
• ? gt 95 (TT)

Inner Tracker 11 planes of RPCs
Precision tracker 6 planes of drift tubes
21 bakelite RPCs (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)
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nt detection (OPERA)

• Detection Efficiency

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nt backgrounds

• Cut on invariant mass of primary tracks

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nt events expected (OPERA)
?m2 ( x 10-3 eV2) ?m2 ( x 10-3 eV2) ?m2 ( x 10-3 eV2) Back- ground
1.9 2.4 3.0 Back- ground
? ? 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

• Comparison
• 4 nt events
• over 0.34
• background
• at
• DONUT
• .27kton

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Outstanding Issues
Emulsion Sampling

• If LSND signature is oscillations, nt appearance
  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?