Tsuyoshi Mase, S TEL Nagoya Univ ersity for the LHCf collaboration
1 The OPERA emulsion detector for a long-baseline neutrino oscillation experiment H.Shibuya Toho...
-
Upload
thomas-carroll -
Category
Documents
-
view
222 -
download
0
Transcript of 1 The OPERA emulsion detector for a long-baseline neutrino oscillation experiment H.Shibuya Toho...
1
The OPERA emulsion detector for a long-baseline neutrino oscillation experiment
H.Shibuya Toho Univ., Japan
K.Hoshino, M.Komatsu, K.NiwaNagoya Univ., Japan
S.Buontempo, A.Ereditato, G.Fiorillo, P.Migliozzi, P.Strolin
Naples Univ. and INFN, Italy
G.RomanoSalerno 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
2
Physics process: neutrino oscillation
-
h-n
e- e+--n
- + X
CC
appearance esperiment direct decay detection
PPosc osc = sin= sin2222 sin sin22((1.27 1.27 xx mm22((eVeV22) ) xx L( L(kmkm)/E()/E(GeVGeV))))
mm22minmin= (P= (Poscosc//2) 2) xx 1/1.27 1/1.27 xx E/L E/L
3
New results from Super Kamiokande and CHOOZ: importance of -oscillation search
OPERA L.o.I: study the atmospheric neutrino anomaly, as indicated by
Kamiokande large mixing and m2 ~10-2 eV2
amiokande
SuperK.
--e
CHOOZ
4
Explore the possibility of a higher sensitivity search:
exploit high intensity of the beam under study
increase of detector mass (modularity)
Perform the exercise with reference options:
optimization will be needed:
beam, detector design
Assess the feasibility of the experiment: tests
background reduction, emulsion handling, technical issues
s there room for improvements ?
5
Automatic emulsion scanning
• Pioneered by the Nagoya group: Track Selector speed about x 100 w.r.t. semi-automatic systems
• New Track Selector routinely scanning in Japan and starting-up in
Napoli speed about x 10 w.r.t. Track Selector
• Other CHORUS laboratories actively scanning
• R&D going on at CERN, Nagoya, Napoli and Salerno
6
Microscope event view
Emulsion
to beam
Good tracks appear as dots
Tracking implies
connection of dots
in different layers
~100 m
7
Track selector ~
10
0
m
(emulsion beam)
T
8 Aim, target mass and experimental technique
• Atmospheric neutrinos (SK) mm22 sensitivity 10 sensitivity 10-2-2 -10 -10-3-3 eV eV22
• 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)
determined by the angular cuts: (resolution) 20 < 20 < kinkkink < 500 mrad < 500 mrad (scanning & bg rejection)
• BR e, h 0.174 , 0.178 , 0.4980.174 , 0.178 , 0.498 • Fiducial cuts & alignment geomgeom~ ~ 0.930.93
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
23
B.G. reduction by vertex kinematics
• Before kinematical analysis of candidate events
Nbg(h-) ~ 2 events Nbg(-) + Nbg(e-) ~ 0.5 events
Nbg(associated charm) ~ 0.4 events
• Vertex kinematics: aim Nbg ~ Nbg / ~5 (to be studied)
Nbg (charm) < 1 event
Important : vertex kinematics require track before decay possible only with emulsion granularity
24Sensitivity and discovery potential
CC / x BR vert
sin2 2 ( large m2 ) < 2 x 2.3 / (14930 x 0.48 x 0.36 x 0.90)
< 2 x 10-3
m2 (full mixing) < 10-3 eV2
(90% CL)
f oscillation occurs :m2 = 2 x 10-3 eV2 ~ 10 detected events
m2 = 5 x 10-3 eV2 ~ 50 detected events
NO OBSERVED EVENTS
total b.g. :~ 1 event
25
• ~ 20000 events NC+CC to be scanned (achievable with fast automatic microscopes)
• rougher event localization w.r.t. short baseline exp. (allowed by low track density)
• fast general scanning (downstream ES): over ~1 cm2
• scan back of all found segments up to the vertex
• scanning more elaborate, special care for candidates
• exploit on-going progress and equipment for CHORUS
Emulsion scanning (1)
26
Emulsion scanning (2)
• ~ 20000 events/4 years ~ 5000 /100000 bricks removed per year• aim: emulsion developed and “quasi on-line” scanning
• replace bricks (?)
• fading “regenerates” the emulsion left in place
Prompt physics analysisEmulsion experiment with a long-life
develop emulsion
27Feasibility studies, optimization and R&D (1)
• Emulsion diluted emulsion: diluted emulsion: quality vs. costquality vs. cost procurement & handling procurement & handling ES manufacturing: ES manufacturing:
dedicated pouring machine (industry?), X-ray dedicated pouring machine (industry?), X-ray filmsfilms
controlled fadingcontrolled fading
• Bricks passive material: passive material: Pb vs. Fe, radioactivityPb vs. Fe, radioactivity spacers (plastic, honeycomb, ....): spacers (plastic, honeycomb, ....):
low density, rigidlow density, rigid vacuum vs. mechanical packing (both ?) vacuum vs. mechanical packing (both ?) optimize dimensions: optimize dimensions: Montecarlo + prototype Montecarlo + prototype
teststests
• 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
28
Feasibility studies, optimization and R&D (2)
• Apparatus design optimize module (supermodule) dimensions optimize module (supermodule) dimensions and layoutand layout
temperature and humidity control temperature and humidity control detector mass and cost detector mass and cost
spectrometer design: spectrometer design: performance requirementsperformance requirements
• 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,
hit density, optimize layer thicknesshit density, optimize layer thickness beam tests: beam tests: kink efficiency, angular resolution, kink efficiency, angular resolution, vertex findingvertex finding
• R&D emulsion: emulsion: collaboration with industrycollaboration with industrypouring machines pouring machines dedicated scanning systems: dedicated scanning systems: fast general fast general
scanningscanning
• Beam optimize beam design: optimize beam design: intensity, spectrum, <E>intensity, spectrum, <E>
29
A possible schedule for OPERA
• 1997 LoI: studies, conceptual design• 1998 Tests, feasibility, design,
proposal• 1999 Approval, prototypes, tests• 1999-2002 Construction• 2002 Start neutrino data taking• 2003 Early physics results
30
at Gran Sasso
• Possible design: ~750 ton , 2.5 x 1020 pot (4 years)
~20000 CC+NC events
• Discovery potential: small bg, a few events are meaningful:@ Super K. (m2 = 5 x 10-3 eV2) 50 events (~1 b.g.)
• Negative search: m2 < 10-3 eV2 ; sin2 2 < 2 x 10-3 covers atm (Super Kamiokande)
• Modular structure: detector staging is possible
High sensitivity - search
explore the atmospheric neutrino signal
31
ConclusionsConclusions
• Promising technique to detect - oscillation with a Long Baseline Experiment at the Gran Sasso
• Further studies, tests and R&D needed to assess the feasibility of the experiment
• Explore the parameter region m2 > 10-3 eV2
to determine the source of the atmospheric neutrino signal