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

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


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!


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


Making a Neutrino Beam

• Conventional Beam

• Beta Beam

• Neutrino Factory

2For each of these beams,

flux (Φ) is related to boost of parent particle ()


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


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:


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


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!


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


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)


View of the inner detector

Half Module of ICARUS


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


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


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


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+


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


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


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


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


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


detection (OPERA)

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


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


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


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


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)


detection (OPERA)

• Detection Efficiency


backgrounds

• Cut on invariant mass of primary tracks


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


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

Documents

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