Emulsion detector at a Neutrino Factory Detector Working Group, Aug. 21 st, Irvine, California...
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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