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

2

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

3

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

4

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

5

The Site

6

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)

7

Separate cable string (station).Connections are done on dry

ice slot

cable

tractor with ice cutter cable layer

Deep Water Optical Properties

8

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

9

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

10

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 !

11

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

12

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

13

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

14

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

15

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

16

NT200+ data analysis is ongoing

completed in 2005

Laser pulses as HE cascades

17

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)

18

• 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

19

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

20

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

21

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

22

23

Thank You

Ice camp view from shore. April 2009