Emulsion detector at a Neutrino Factory

Detector Working Group, Aug. 21st, Irvine, California

Giovanni De Lellis

University of Naples “Federico II”

on behalf of the ECC WG

Outline of the talk

• Revise the potentiality of using an ECC detector to study the silver channel

• Use nuclear emulsions in a magnetic field

• MC simulation to validate the perfomances

• Experimental tests performed

• Perspectives of the technique

• Current limitations

The physics case: synergy of golden and silver channels

• Study the CP violation in the leptonic sector: e µ the most sensitive (“golden”) channel

• In the (13,) measurement, ambiguities arise– Intrinsic degeneracy [Nucl. Phys. B608 (2001) 301] m2 sign degeneracy [JHEP 0110 (2001) 1]

– [23, /2 -23] symmetry [Phys. Rev. D65 073023 (2002)]

• The “silver” channel (e and µ) is one way of solving the intrinsic degeneracy at the neutrino factory– A. Donini et al., Nucl. Phys. B646 (2002) 321.

• An hybrid emulsion detector is considered– D. Autiero et al., Euro. Phys. J. C33 (2004) 243

Golden and silver channels

truemeas

90,1:parametersInput 13

ambiguities

Solving the ambiguities

A hybrid emulsion detector

8.3kg

10 X0

Pb

Emulsion layers

1 mm

10.2 x 12.7 x 7.5 cm3

• Target based on the Emulsion Cloud Chamber (ECC) concept• Emulsion films (trackers) interleaved by lead plates (passive)• At the same time capable of large mass (kton) and high spatial resolution (<1m) in a modular structure

The basic unit : the « brick »

ECC topological and kinematical measurements• Neutrino interaction vertex and decay topology reconstruction• Measurement of hadron momenta by Multiple scattering• dE/dx for /µ separation at the end of their range• Electron identification and energy measurement• Visual inspection at microscope replaced by kinematical measurements in emulsion

8 GeVECC technique successfully used in cosmic rays (X-particle discovery in 1971) and by

DONUT for the direct observation

Electronic detector task

supermodule

8 m

Target Trackers

Pb/Em. target

ECC emulsion analysis:

Vertex, decay kink e/ ID, multiple scattering, kinematics

Extract selected brick  

Pb/Em. brick

8 cm Pb 1 mm

Basic “cell”

Emulsion

trigger and locate the neutrino interactions muon identification and momentum/charge measurement

Electronic detectors:

Brick finding, muon ID, charge and p

Link to muon ID,Candidate event

Spectrometer

p/p < 20%

Topology and kinematics of signal and background

edunidentifi

C

Punch throughor decaying

NC

Charge misidentification: 1-3 x 10-3

iedmisidentif

from oscillation

Background

732 km

3000 km

signal

charmdecay in flight and

punch-through

+

Signal and background versus E

Emulsion scanning• Real time analysis: several tens of bricks

extracted/day• High speed (20 cm2/h) fully automatic scanning

systems (one order of magnitude faster than previous generation)

• independent R&D in Europe and Japan based on different approaches

• First prototype developed and tuned in Europe• Successfully running since Summer 2004 with

high efficiency (>90%), high purity (~2 tracks/ cm2 /angle) and design speed

• 2 mrad accuracy at small incident angles

Fast CCD camera (3 k frames/sec) Continuous movement of the X-Y stage

Emulsion Scanning load• Boundary conditions:

– 1 Kton detector located 732 km from the beam source– 5 years data taking

• Scan all events with a negative (wrong sign) µ : – “silver” ~ 30 events and “golden” ~ 310 – Anti-µ with misidentified charge: ~ 2200 – Charm background: ~ 80 events NC with punch-through or decaying h: ~ 4800

• ~ 8 x 103 events in 5 years• 10 kton ECC detector feasible

CHORUS DONUT OPERA

0.008

0.25

3

60

0.001

0.01

0.1

1

10

100

TS(TTL) NTS(CPLD)UTS(FPGA) S-UTS

Scanning System Historyviews/sec(1view=120×90m2)

European scanning system

Combining ECC @ 732km and iron @ 3000km

No clone regions for 13>1°, for 13=1° they show-up in

less than 10% of the experiments

5 kton ECC + 40 kton Iron Allowed regions from the analysis of simulated data for 13 = 1°, = 90°. The best fit

is 13 = 0.9°, = 80°.

Both at 3000 km

•Large reduction of all backgrounds ( 1/L2) except the muonic decay of + events from anti-µ anti- •scanning load reduced by about a factor of 20

dE/dx measurementNIM A516 (2004) 436

Pb Film

P=1.2GeV/c

Hadron+

@KEK/PS

dE/dX

dE/dx = measurement

~number of grains

P

Electron energy measurement

MC Data

)(E

4.0~

GeV

@ a few GeVEnergy determination

by calorimetric method

Test exp. @ CERN

Momentum measurement by Multiple Scattering

Nucl. Instr. Meth. A512 (2003) 539

3 GeV pions 2 GeV pions

30% resolutionwith 3 X0

22% resolutionwith 5 X0

Routine scanning performed

Position and angular accuracy: NIM A554 (2005) 247

X projection Y projection

0.05 µm

Straight tracks (up to 50 mrad)

Median ~ 0.4 mrad

200 mrad inclined tracks

0.6 mrad

300 mrad inclined tracks

0.9 mrad

Residual of base tracks w.r.t. fitted tracks

Using precise meausurements p measured with 15-20% accuracy up to 6 GeV

12

2

/

/

2

/

/

/2

N

i

ii

i

ii

e

ey

e

ex

e

2 GeV : data

4 GeV : data

2

0/

2

/ )(

6.132

X

d

zPee

/e separation study:2 = 2e -2

separator

6 GeV : data-MC comparison

Emulsion detector in a magnetic field

• Measure the charge and momentum

• The charge determination allows the extension of the silver channel to the non-muonic decays (BR gain)

• Study the feasibility of the “platinum” channel (µe) by means of the charge determination and electron identification capabilities

Magnetized ECC structure

We have focused on the “target + spectrometer” optimization

Electronic det:e//µ separator

&“Time stamp”

Rohacell® plateemulsion films35 stainless steel plates

spectrometer

target

shower absorber4.5 cm, 2 X0

Structure optimization

• To be optimized: spacer thickness (25 cm) and magnetic field (0.25 1 T)

• Using muons with momentum from 1 to 10 GeV• In the evaluation of the performances, true and

reconstructed momentum are compared downstream of the target region (beginning of the spectrometer) except when using the Kalman filter

4 GeV µ momentum resolution

4 GeV µ charge misidentification

µ end electron momentum resolution: 3 gaps (3cm thick) and 0.5 T

For the electron only hits associated to the primary electrons used in the parabolic fit (Kalman not used)Given the non negligible energy loss in the target, the electron energy is taken downstream for the comparison of true against reconstructed

µ electron

µ and electron charge mis-identification:3 gaps (3cm thick) and 0.5 T

µ electron

Experimental test for a M-ECC

Compact ECC structure

Chika FukushimaS. Ogawa, M. Kimura, Hiroshi Shibuya, Koichi Kodama, Toshio Hara

Dec. 2005 KEK-PS T1 line

•Different support used (40 μm polystyrene or 200 μm acrylic plate)•2 GeV + [without magnet] 3000/cm2 as reference beam•1 T magnetic field•Different momentum: 0.5, 1 and 2 GeV, each with 1000/cm2 + ( -)

The sagitta method

L = 3 cm in this study

Preliminary experimental results • The relative error is roughly

ds/s = 0.20 0.029 p [GeV/c]• ds/s should be about 0.35 in

the case of p = 10 GeV/c• Assuming a Gaussian

distribution, the charge mis-identification probability for a 10 GeV lepton ~ 0.2%

• N.B. Multiple Coulomb scattering has larger tails The probability of the charge mis-identification should be somewhat larger

Difference with the proposed geometry:Better plate to plate alignment (few µm instead of 10 µm) ++

2 gaps instead of 3 --Gap width 1.5 cm instead of 3 cm --

Possible design of a far detector• Assume transverse size 15.7x15.7 m2 (as Nova)• A brick contains 35 stainless steel plates 1 mm thick: it corresponds to

about 2 X0 • The spectrometer part consists of 3 gaps (3 cm each) and 4 emulsion

films• Brick weigh 3.5 kg• A wall contains 19720 bricks 68 tons• 60 walls 1183200 bricks 4.1 kton• Emulsion films are 47.3 M pieces (12 M in OPERA)• Assuming as electronic detector 35 Nova planes (5.3 X0 ) after each

MECC wall 2100 planes• The total length of the detector would be ~ 150 m• Synergy with other detectors for the silver and platinum study

Signal (θ13=2°,δ=0°)

Signal (θ13= 2°, δ=90°)

Background

L=732km old 2.1 7.2 23.9

L=3000km old 2.8 5.1 2.4

L=732km new 6.4 21.5 60

L=3000km new 8.4 15.3 6.0

Silver channel sensitivity

Very preliminary

Conclusion and outlook• A hybrid detector for the CP violation study in the

leptonic sector is feasible by means of the “silver” channel

• A magnetized ECC with stainless steel has also been presented

• Modular structure allows to test it with a single brick• First experimental tests are very encouraging • A far detector (4 Kton target) with this technique has been

presented• The choice of the electronic detector brings interesting

synergies• Big question mark: how to magnetize so large volumes• Study the µ identification with the electronic detector• Check the sensitivity to the “golden” channel• A full simulation of neutrino interactions mandatory to

evaluate the oscillation sensitivity