Liquid Scintillator Technology Tobias Lachenmaier Universitt - - PowerPoint PPT Presentation
Liquid Scintillator Technology Tobias Lachenmaier Universitt Tbingen 11th International Workshop on Next Generation Nucleon Decay and Neutrino Detectors December 13-16, 2010, Toyama, Japan Outline The LENA project Detector layout
Tobias Lachenmaier Universität Tübingen
11th International Workshop on Next Generation Nucleon Decay and Neutrino Detectors December 13-16, 2010, Toyama, Japan
Liquid scintillator 50 kt LAB/PPO+ bisMSB Inner vessel (nylon) Radius r = 13m Buffer 15kt LAB, Δr =2m Cylindrical steel tank, e.g. 55000 PMTs (8“) with Winston Cones (2x area) r = 15m, height = 100m,
Water cherenkov muon veto 5,000 PMTs, Δr > 2m to shield fast neutrons Cavern egg-shaped for increased stability Rock overburden: 4000 mwe
Desired energy resolution → 30% optical coverage → 3000m² effective photo- sensitive area Light yield ≥ 200 pe/MeV The tracking option adds to the requirements of the PMT array and electronics: → more, but smaller, faster PMTs → full waveform digitizing
Pyhäsalmi design
Supernovae
Antielectron n spectrum with high precision Electron n flux with ~ 10 % precision Total flux via neutral current reactions Separation of SN models independent from (collective) oscillations in NC reactions
ca 15.000 events for a galactic SN high statistics energy dispersive time dispersive flavour resolving
For “standard“ SN (10kpc, 8M):
Channel Rate Threshold (MeV) Spectrum ne p → n e+ 8900 1.8 ✓ ne
12C →12N e-
200 17.3 (✓) ne
12C →12B e+
130 13.4 (✓) n 12C →12C* n 860 15.1 ✗ n p → p n 2200 1.0 ✓ n e- → e- n 700 0.2 ✓ _
Michael Wurm, TUM Physics with LENA 6/24
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Astrophysics
flavor-dependent spectra and luminosity, time-dev.
by envelope matter effects
Michael Wurm, TUM Physics with LENA 7/24
Astrophysics
flavor-dependent spectra and luminosity, time-dev.
by envelope matter effects
Michael Wurm, TUM Physics with LENA 8/24
Neutrino physics
neutronisation burst Pee ≈ 0 → normal mass hierarchy
the SN envelope: hierarchy, q13
n mass hierarchy, q13
neutrino oscillations
Regular galactic Supernova rate: 1-3 per century intergrated neutrino flux generated by SN on cosmic scales
current neutrino experiments In LENA: 4-30 ne events per year (in 50kt target mass) _
Detection via Inverse Beta Decay ne+p n+e+ allows discrimination of most single-event background limiting the detection in SK Remaining Background Sources
_ _ Scientific Gain
Expected rate: 2-15 ev/year in fid. vol. (in energy window from 10-25MeV)
(18kt) Detection Channel elastic ne scattering, E > 0.2MeV Background Requirements
(as achieved in Borexino)
for CNO/pep-n measurement Scientific Motivation
(e.g. metallicity, contribution of CNO)
7Be-n (on a per mille level)
transition region → new osc. physics
_
[Borexino, arXiv:0805.3843] 7Be-n
CNO/pep-n
11C 85Kr 210Bi
Detect anti-neutrinos of the U, Th decay chains (inverse b-decay energy threshold is 1.8 MeV). Expected event rate at Pyhäsalmi : 2000 events/year in 50 kt Background from reactors: 700 events/year in 50 kt in the relevant energy window ► measure flux from crust and mantle ► determine U/Th ratio ► disentangle continental/oceanic crust with more than one detector location ► only detector within LAGUNA able to detect geo-neutrinos
Michael Wurm, TUM Physics with LENA 13/24
improve at least factor of 10.
Simulated energy spectrum of 20000 proton decay events into Kaon channel (light yield 180 p.e./MeV) Two peaks:
~ 257 MeV
Energy-cut efficiency E=99.5%, bound protons of 12C included.
Variety of other channels can be tested.
Potential at higher energies depends on tracking and PID capabilities (all ionizing particles are visible) HE particles create along their track a light front very similar to a Cherenkov cone. Single track reconstruction based on:
Sensitive to particle types due to the ratio of track length to visible energy. Angular resolution of a few degrees, in principal very accurate energy resolution.
entry point exit point
exit point
muon time-of-flight Cherenkov-like light-front of the muon is visible in the Inner Detector!
tracks from CNGS beam in Borexino
real data!
actually a low E calorimetry detector; not optimized for tracking at all
designed for tracking capability
Michael Wurm
particles resembles a Cherenkov cone → directionality → can use arrival time of first photons on PMTs and total photon count for tracking
beams and atmospheric neutrinos
reconstruction programs for tracking:
Geant4 LENA optical detector model by D. Hellgartner
value of photon pattern depending on all track parameters
100-500 MeV single-track muons: very good track reconstruction with < 1+/-2cm position uncertainty and 0.1+/-0.1ns time uncertainty for the starting point and 2.5° on direction 100-750 MeV single-track electrons: all uncertainties comparable to muon events but for some events, the direction is reconstructed with wrong sign (starting point at end of track). We are working on this right now.
electrons (1.2 GeV) muons (1.2 GeV)
Muon-decay electron:
sufficiently late
spallation neutrons
>99.63% (95%C.L.)
Pulse-shape discrimination:
more powerful for ne selection
The main fit routine maximizes probability of charge and arrival time PDFs: First estimate is used as input. Energy fit:
photon number per PMT, includes:
DE/E = 9%/sqrt(E/MeV)
DE/E ≈ 0.5%
The main fit routine maximizes probability of charge and arrival time PDFs: First estimate is used as input. Track fit:
log-likelihood maximization
Df = 3.1°, Dxorigin = 2cm
CC neutrino reaction cross-sections on Carbon, MiniBooNE, hep-ex/0408019
CC events from HE n‘s usually involve:
E < 1 GeV
E = 1-2 GeV
E > 5 GeV Resulting light front/PMT signals are superposition of single-particle tracks. Multi-Particle Approach:
(Juha Peltoniemi, arXiv:0909.4974)
combinations of test particle tracks.
tracking as input.
information of the individual PMTs to discern the particles.
capture processes (n‘s) provide additional information.
Single Tracks:
for 2-5 GeV range, depends on particle, read-out information Multiparticle Events:
Michael Wurm, TUM Physics with LENA 28/24
2GeV nm quasielastic scattering 4GeV nm deep-inelastic scattering
Baseline
(>103 km for mass hierarchy)
Beam properties
Preliminary GLoBES result
hierarchy for sin2(2q13)>5x10-3
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Michael Wurm, TUM Physics with LENA 29/24
100 kt would be better
<5% does not improve results
(<10% reduction in target mass)
beam contamination is the bottle-neck
p+ p- P m- nm
ROCKPLAN, Finland, together with TU München: pre-feasibility study for a LENA detector at Pyhäsalmi
depth of 1400-1500 m possible geological study completed vertical detector position infrastructure (ventilation,
electricity, etc.) considered
construction time of cavern ~ 4 yrs first cost and time estimate for the
whole project
excavation study for Pyhäsalmi
substantial improvements
and extra structures to fulfill safety requirements:
tunnel, 1 or 2 new shafts
stability simulations
→ elliptical horizontal
cross-section and kink in vertical cross- section
Water Cherenkov detector
Conventional Steel Tank + well known, straightforward to build, robust
elements and connections Sandwich Steel Tank + cost effective, room for cooling, fast install, laser welds
mechanically challenging Sandwich Concrete Tank + well known, straightforward to build, robust, improved physics
Hollow Core Concrete Tank + room for cooling, mechanically strongest, improved physics, quick build
pumping
(„Winston Cones“) to increase effective area of PMTs by a factor of ca. 2 → increases number of detected photons / MeV deposited → increased resolution
acceptance angle → can be used to limit field of view to fiducial volume
detector performance with the optical Geant4 Monte Carlo simulation of LENA
Borexino Winston Cone CTF Winston Cone
shielding into design
Borexino encapsulation with pressure- resistant window instead of thin PET foil window
Baseline
(>103 km for mass hierarchy)
Beam properties
Preliminary GLoBES result
hierarchy for sin2(2q13)>5x10-3
_
Baseline
(>103 km for mass hierarchy)
Beam properties
Preliminary GLoBES result
hierarchy for sin2(2q13)>5x10-3
_
3s discovery potential 2s 1s
3s discovery potential 2s 1s
Consortium composed of 21 beneficiaries in 9 countries 9 university entities (ETHZ, Bern, Jyväskylä, OULU, TUM, UAM, UDUR, USFD, UA) 8 research organizations (CEA, IN2P3, MPG, IPJ PAN, KGHM CUPRUM, GSMiE PAN, LSC, IFIN-HH) 4 private companies (Rockplan, Technodyne, AGT, Lombardi) Additional university participants (IPJ Warsaw, Silesia, Wroclaw, Granada)