1 The OPERA emulsion detector for a long-baseline neutrino oscillation experiment H.Shibuya Toho Univ., Japan K.Hoshino, M.Komatsu, K.Niwa Nagoya Univ., Japan S.Buontempo, A.Ereditato, G.Fiorillo, P.Migliozzi, P.Strolin Naples Univ. and INFN, Italy G.Romano Salerno Univ. and INFN, Italy Y.Sato Utsunomiya Univ., Japan LNGS-LOI 8/97 and SPSC 97-24/I218 Presented by: A.Ereditato, INFN Naples M.Komatsu, Nagoya Univ. Gran Sasso Laboratory, 6/2/1998
31
Embed
1 The OPERA emulsion detector for a long-baseline neutrino oscillation experiment H.Shibuya Toho Univ., Japan K.Hoshino, M.Komatsu, K.Niwa Nagoya Univ.,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
The OPERA emulsion detector for a long-baseline neutrino oscillation experiment
• CERN-Gran Sasso beam M = M = OO (1000) ton (1000) ton
• Impossible with pure emulsion target (CHORUS ~ 0.8 ton , TOSCA ~ 2.5 ton)
• New technique required iron (lead)-emulsion sandwich: iron (lead)-emulsion sandwich: passive target material, emulsion for trackingpassive target material, emulsion for tracking
• Starting point : the EEmulsion CCloud CChamber (ECCECC)
9
Rethinking the ECC technique
• Charm decays and hadron reinteractions in the passive material : unacceptable backgrounds using impact parameter
• Hence, no impact parameter, no decays in Fe (Pb)
• The OPERA* detector concept**
• Charm decays and hadron reinteractions in the passive material : unacceptable backgrounds using impact parameter
• Hence, no impact parameter, no decays in Fe (Pb)
• The OPERA* detector concept**
*) OOscillation PProject with EEmulsion tRRacking AApparatus
**) A. Ereditato, K. Niwa, P. Strolin, INFN/AE 97/06
- select -decays in gaps between metal plates- minimal plate thickness () , 2 emulsion sheets- measure decay “kink” in space, by emulsion tracking
10
L E B E G E B E L0
5
10
15
20
25
30
35
40
45
L E B E G E B E L
Decays %
Fraction of ’s decaying in:L (lead), E (emulsion layer), B (base), G (gap), L (long kinks)
For m2 = 2 x 10-3 eV2 and 1 mm lead, 3 mm gap
11
The detector
• Lead-emulsion target - element: 1 mm Pb, ES, 3 mm gap, ES1 mm Pb, ES, 3 mm gap, ES - brick: stack of 30 elements (~ 13 cm thick, 15 x 15 cmstack of 30 elements (~ 13 cm thick, 15 x 15 cm22 X-sect.) X-sect.) - module: 18 x 18 bricks ( ~ 2.8 x 2.8 m18 x 18 bricks ( ~ 2.8 x 2.8 m22 ) ) - electronic detector planes following each module (~ 5 cm thick)(~ 5 cm thick) - 300 modules: ~ 750 ton, subdivided into 10 identical supermodules~ 750 ton, subdivided into 10 identical supermodules - overall target dimensions ~ 3.5 x 3.5 x 40 m~ 3.5 x 3.5 x 40 m3 3 (x 2)(x 2)
• Muon detection - tracking in the target (electronic detectors) - magnetised iron -spectrometer downstream: sign of charge (momentum)• Calorimetry - in the target: Pb (each module ~ 5 XPb (each module ~ 5 X0 0 ) + electronic det. (RPC, straws,...)) + electronic det. (RPC, straws,...)
• p/p ~ ~ 10-20 % at 1-30 GeV/c10-20 % at 1-30 GeV/c from multiple scattering in emulsion
Preliminary design
12
element brick
1mm
3 mm
150
mm
150 mm
135 mm
13
front view
12.5 m
5 m
14
apparatus5m
3.5m
~ 45 m
15
Emulsion
• No target (“bulk”) emulsion, but still ~ 13 m3 of emulsion layers
• Diluted emulsion: AgBr content 1/2-1/3 w.r.t. short
baseline experiments: cost scales down (lower grain density allowed by automatic scanning and b.g. level)
• Industrial production: time schedule, lower cost
• Alternative: similar emulsion as for X-ray films
• R&D on emulsion: tests on prototype ES and bricks going on in Nagoya and Fuji company
16
Electronic detectors
• “Moderate” position resolution (shower center): ~ few mm (low background tracks)
• Standard large-surface trackers can be used:
Resistive Plate Chambers,
Honeycomb chambers,
Streamer tubes.....
• Need reconstruction behind each emulsion module:
(i.e. using RPC’s) ~ 7000 m~ 7000 m2 2 total detector surfacetotal detector surface
• Similar detectors may be used for the muon spectrometers
17
Data and event reconstruction
• Study e-, - , h- , (possibly 3• Track localization by electronic detectors
• Start scanning from ES upstream of event in electronic detector
• General scanning and scan back in ES
• Find vertex plate (Pb) and neutrino vertex
• Follow down tracks from vertex
• Kink search (in gaps between Pb)
• Kinematics of candidate events (few % of total)
downback
Start scanning here
18
interactions
• Scale reference option: 5 x 105 x 1019 19 pot/a , 75% efficiency, 220 days runpot/a , 75% efficiency, 220 days run
assume 2.5 x 102.5 x 1020 20 pot/4 yearspot/4 years
• Data: ~ 810 CC ~ 810 CC interactions/kton x 10 interactions/kton x 101919 pot pot (Gran Sasso)(Gran Sasso) ~ 15000 CC in 4 years ~ 15000 CC in 4 years (750 ton detector)(750 ton detector)
~25~25 interacting in OPERA ( interacting in OPERA (mm22 = 2 x 10 = 2 x 10-3-3 eV eV22))
~150~150 ““ ( (mm22 = 5 x 10 = 5 x 10-3-3 eV eV22))
possible improvements bydesign optimization
19
detection efficiency
• Decays outside Pb (1 mm) gapgap~ ~ 0.500.50
gap depends on beam features)0.87 (0.87 ( • Kink finding efficiencykink0.84 (0.84 ( e) e) 0.89 (0.89 ( h) h)
Total efficiency for the 1-prong channels: 0.36(3 channel under study)
20
background
h-
signal
-
D+
neutrals
- (undetected)
h+
Charm induced background
(sign of daughter only measured if muon)
21
Charm b.g. to - h-, -, e-
(before vertex kinematics of candidate events)
= 0.0560.056 charm / CC
x 0.370.37 D production probability
x 0.3060.306 BR (D h + neutrals)
x 0.470.47 D decay outside Pb
x 0.860.86 kink
x 0.930.93 fiducial cuts & alignment
x 0.050.05 - CC not identified x 1490014900 CC events ~ 1.8 events (h-)
BR (charged D l + neutrals) ~ 0.0750.075
charge measured by the downstream
spectrometer (1- ~ 0.30.3)
~ 0.2 events (-)
~ 0.4 events (e-)
Total: 2.4 events from charm
Nbg(h-)
22
Other backgrounds
• Prompt in the beam: negligiblenegligible (10-6 level)
• Hadron reinteractions : a few kinks in the spacer are rejected rejected by the kink angle cut (20 mrad) and by by the kink angle cut (20 mrad) and by
the detection of heavy fragmentsthe detection of heavy fragments
• , K decays (CC and NC) : events (further reduced by possiblereduced by possible
momentum cutmomentum cut)
• NC associated charm production : double decay topology: 0.4 events before the vertex kinematicsbefore the vertex kinematics
• Electronic trackers define requirements: define requirements: space & time resolutionspace & time resolution optimize performance vs. cost optimize performance vs. cost
industrial production industrial production tests on prototypes: tests on prototypes: track association to emulsiontrack association to emulsion
• Tests prototype bricks: prototype bricks: mechanics & structuremechanics & structure install bricks in the Gran Sasso Laboratory: install bricks in the Gran Sasso Laboratory:
ambient radioactivity, alignment by ambient radioactivity, alignment by cosmics, cosmics,
• R&D emulsion: emulsion: collaboration with industrycollaboration with industrypouring machines pouring machines dedicated scanning systems: dedicated scanning systems: fast general fast general