Lake Baikal: from Megaton to Gigaton
Bair Shaybonov, JINR, Dubna
on behalf of the Baikal Collaboration
TAUP09, Rome, July 2009
Outline
Status of the Baikal Detector
Selected Results obtained from NT200 array data
Activity towards Gigaton Volume (km3 scale) Detector
Summary
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Baikal Collaboration
Russia (7 institutes), Germany (1 institute):• Institute for Nuclear Research RAS, Moscow,
• Irkutsk State University,
• Skobeltsyn Institute of Nuclear Physics MSU, Moscow,
• DESY - Zeuthen
• Joint Institute for Nuclear Research, Dubna,
• Nizhny Novgorod State Technical University,
• St.Petersburg State Marine University,
• Kurchatov Institute, Moscow.
~50 authors
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Present Status
NT200 array: 192 Optical Modules8 Strings6.5 m between Modules20 m between strings
NT+ array:36 Optical Modules3 distant Strings
New technology string:12 Optical Modules10 m between Modules
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All parts work in joint regime
Project Milestones: > 1983 Site and Water studies;
R&D: large area PMT, underwater technology,Small physics setups (exotics search)
1993 NT36 – the first underwater array operates
... stepwise upgraded (w/ physics operation)
1998 NT200 commissioned and is operating
2005/06 Upgrade to NT200+ completed and is operating
> 2006 R&D activity for a Gigaton Volume Detector in Lake Baikal
2011 Start of GVD cluster prototype
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The Site
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NT+ String 1Cable Station
NT+ String 3 NT+ String 2NT200 Strings
Ice as a natural deployment platform is available ≈2 monthes/year:
Telescope upgrades & maintenance
Test & installation of new equipment
Electrical winches used for deployment operations
All connections are done on dry.
NT200+ deployment from 1m thick ice,
4km off-shore.
Cable Laying on the Lake BedRelatively simple laying technique, because of:
Stable ice cover
Close to shore (3.6 km)
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Separate cable string (station).Connections are done on dry
ice slot
cable
tractor with ice cutter cable layer
Deep Water Optical Properties
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Abs.Length: 22 ± 2 m Scat.Length: 30-50 m
<cosθ>: 0.85-0.90
No high luminosity bursts from biology
Baikal
Baikal
, nm , nm
- 8 strings- 192 optical modules
= 96 pairs (coincidence)- Time + Charge measured
- σT ~ 1 ns- dyn. range ~ 1000 p.e.
Effective area: 1 TeV ~ 2000 m² Eff. Shower volume: 10 TeV ~ 0.2 Mton
1 PeV ~ 1Mton
NT200 Array
Quasar PMT: 37cm (14.6”),
hybrid, mushroom shapeHeight = 70m, = 42m Vinst = 0.1 Mton
0
0
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NT200 Array – Physics Results
Low Energy Phenomena:
Atmospheric neutrinos
WIMP neutrinos from Earth center
from the Sun
Search for Exotic Particles:
Relativistic magnetic monopoles
High-Energy Phenomena:
Diffuse neutrino flux
GRB neutrinos
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NEW
NEW
NEW
Data Sample:1998-2002 (Apr98 – Feb03)
= 1038 live days
NT200+ data analysis is ongoing
Diffuse Flux LimitsNew analysis of existing data with vertex, energy and direction reconstruction of cascades: improvement of published
limit by a factor of ~ 3 !
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Model Model rejection factor n90%/Nmodel
BAIKAL AMANDA
Stecker (05) 3.4 1.6
Mannheim (95) pp+pγ 1.4 1.2
Protheroe (96) pγ 0.5 0.3
Mannheim,Protheroe, Rachen (01)
1.8 0.9
Semikoz,Sigl (03) 1.0 -
The 90% C.L. “all flavour” limit, e:: = 1 1 1
(20 TeV < E < 20 PeV)
E2 Фn < 2.9 ·10-7 GeV cm-2 s-1 sr-1
(Cascades Baikal, 2008)
E2 Фn < 2.2 ·10-7 GeV cm-2 s-1 sr-1 (Muons AMANDA-II, 2007)
E2
Φ(E
), G
eV
cm
-2s
-1sr-
1
Baikal NT200: 1998-02, hard
Baksan’1997
AMANDA-II’2001, hard
MACRO’1998
Super-K’2001
IceCube-22’2007, hard
WIMP Neutrinos from the Sun
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Sun-mismatch angle Ψ (Muon/Sun):
data and background (histogram)
No excess of eventsabove atm. ν BG Flux Limits
- Neutralino (WIMP) as favored Dark Matter candidate - Gravitationally trapped in the Sun (or Earth) - the Sun would be a neutrino-source (annihilation) “Indirect“ WIMP searches
GRB Neutrino Search
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Search for direction + time correlations with 303 GRBs observed by BATSE in 1998-2000, using the upward-going muon data sample.
Time window: (tGRB + T90 + 5s) - (tGRB-5s)Half angle of observation cone: Ψ = 5o
Observed number of events – 1 eventExpected number of bg. events – 2.7 events
SK
Baikal NT200
Amanda-II
“Green’s function” Upper Limits on GRB neutrino fluence (model independent)
F(Eν) = N90% / Seff(Eν)
N90% - 90% C.L. upper limit on the number of events per GRB
Acoustic Studies
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Hydrophones:• 0.5-1.0 mV/Pa• 15-50 kHz
Average noise ≈ 2.5 mPa
θ
Most of bipolar impulses come from lake surface
navigation
wind
• Small noise level would compensate small signal amplitude• Further activity is needed
• 2010 - New string R&D design• 2011 – Tests with acoustic string prototype, first data
Acoustic module allows:• develop technique of acoustic registration• acoustic noise monitoring
since 2006. 150 m depth
Gigaton Volume Detector in Lake Baikal
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Top view
• 12 clusters each 8 strings= 96 strings with 22 – 24 OMs= 2100 – 2300 OMs total
• MC parameters optimization is in progress: H ~ 150 – 300 mR ~ 60 – 100 mZ ~ 15 – 20 m Cluster of strings
Stri
ng
sect
ion
31
5 -
46
0 m
Z ~
15
–2
0 m
NT200+ Array as a first step towards GVD
NT200+ has allowed to verify key elements and design principles of GVD: DAQ, Calibration, Trigger systems, Mechanics
NT200+ is a detector for HE cascades: vertex reconstruction of
cascades has significantly improved -> allows estimate neutrino energy
5 Megaton of enclosed volume
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NT200+ data analysis is ongoing
completed in 2005
Laser pulses as HE cascades
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Laser intensity Cascade energy
1012 – 5 1013 γ/pulse ~ 10 – 500 PeV
Laser reconstruction accuracy:
Position better 1 m
Intensity 6 %
RMS = 2-3 ns
GVD Performance (very preliminary estimations)
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• Cascades detection with E > 100 TeV:dlg(E) ~ 0.1, dψmed < 4o
• Muon detection with E > 10 TeV: dψmed ~ 0.5o
Trig. 5/3 r60_z15_h250
Aeff ≈ 0.20 km2 for 10 TeV
HE muons effective area
Trig. 4/3. min. 2 fired ch. in 1 string
HE cascades effective volume
Veff ≈ 0.25 km3 for 100 TeV
In-situ test of the Prototype String Section 2009
Characteristics:
FADC 200 MHz readout -> Wave form -> Complex events study possible
Switched for joint work with NT200+
Number of optical modules: 12
Type of PMT: XP1807 (12”), R8055 (13”)
Dynamic range: 0.2 … ~100 p.e.
Time window: 5 µs
Time resolution: ≈ 3 ns
Calibration system:
LED Matrix for Time calibration
Two LEDs on each OM for amplitude calibration
External laser source for synchronization with other strings
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The main goals:
• In-situ tests of basic elements of the GVD: new optical modules, DAQ system, new cable communications.
• Studies of the Triggering approach for the GVD.
• Comparison of the classical TDC/ADC approach with a FADC-based full pulse shape readout.
PMT
LEDs
New Optical Module, DAQ development since 2006
Time accuracy of the String Section
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Laser: nearly isotrope light source
OM #1
OM #9
OM #10
Time diff. OM #9 and OM #10
FWHM = 3ns
OM #10
OM #1
Wave forms example
Am
plit
ud
e [
cod
es]
Data processing and analysis are ongoing
Preliminary in-situ tests with underwater laser, LED flasher and muons show good performance of all string elements
Schedule
2009-2010 GVD R&D (supported by Russian foundation)
2010 GVD Technical Design Project
2010-2011 GVD Cluster Prototype
2008-2014 Fabrication (OMs, electronics, cables, etc)
2012-2013 Deployment 0.1-0.3 km3
2014-2015 Deployment 0.3-0.6 km3
2016-2017 Deployment 0.7-0.9 km3
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Summary1. Lake Baikal Experiment has been successfully running since
1993 the first underwater array and first neutrino candidates
2. NT200+ Array is working since 2005 5 Mtons of enclosed volume and improved cascade reconstruction
gives good possibilities to optimize the design and to investigate the key elements of the future GVD
3. We are working hard on tests of the GVD parts and on Technical Design Project sufficient data collected for string section (12 OMs, FADC readout)
since April 2009 and are being analysed
preliminary in-situ tests with underwater laser, LED flasher and muons show good performance of all string elements
GVD Design Project is expected at the end of 2010
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Thank You
Ice camp view from shore. April 2009