STATUS OF BAIKAL NEUTRINO EXPERIMENTSTATUS OF BAIKAL NEUTRINO EXPERIMENT::

Vladimir Aynutdinov, INR RAS, MoscowVladimir Aynutdinov, INR RAS, Moscow for the Baikal Collaborationfor the Baikal Collaboration

HECR’2008 20-22 May 2008HECR’2008 20-22 May 2008

CollaborationCollaboration

Institute for Nuclear Research, Moscow, Russia.

Irkutsk State University, Russia.

Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia.

DESY-Zeuthen, Zeuthen, Germany.

Joint Institute for Nuclear Research, Dubna, Russia.

Nizhny Novgorod State Technical University, Russia.

St.Petersburg State Marine University, Russia.

Kurchatov Institute, Moscow, Russia.

BaikalOutline:

Introduction

Neutrino telescope NT200 (1998 - 2003) Design and Physics Results (selected)

Future Gigaton-Volume (km3-scale) detector BAIKAL-GVD Preliminary Design NT200 upgrade NT200+ (2005 - 2006) Prototype string for BAIKAL-GVD detector (April 2008)

Summary

Baikal - History

• Since 1980 Site tests and early R&D started • 1989/90 Proposal NT200 detector in lake Baikal

submitted• 1993 NT36NT36 started 13.4.93 (36 PMTs at 3 strings)

The First Underwater Array First Neutrino Candidates

• 1998 NT200 commissioned 06.04.98NT200 commissioned 06.04.98 Start full Physics program

• 2005/6 NT200+ commissioned 09.04.05 NT200+ commissioned 09.04.05 • 2006/7 R&D for Gigaton (km3-scale) Volume Detector

(GVD)• 2008 2008 April 2008 - prototype string for GVD was April 2008 - prototype string for GVD was

installedinstalled

The Site

• 4 cables x 4km to shore.• 1070m depth

3600 m

1366

m

NT-200

Absorption length: ~25mAbsorption length: ~25mScattering length: 30-60 mScattering length: 30-60 m

Detection volume >> geometrical volumeDetection volume >> geometrical volume

Ice as a natural deployment platformIce as a natural deployment platform

Ice stable for 6-8 weeks/year: Ice stable for 6-8 weeks/year:

– Maintenance & upgrades Maintenance & upgrades

– Test & installation of new equipmentTest & installation of new equipment

Winches used for deploymentWinches used for deployment

-8 strings: 192 optical modules 96 measuring channels T, Q measure *Timing ~ 1 nsec *Dyn. Range ~ 103 ph.e.

Effective area: 1 TeV~2000m² Eff. shower volume: 10TeV~ 0.2Mt

Quasar : d = 37cmHeight x = 70m x 40m, Vinst=105m3

Low energy phenomena (muons)

- Atmospheric neutrinos

High energy phenomena (cascades) - DDiffuse neutrino fluxiffuse neutrino flux - Neutrinos from GRB - Prompt muons and neutrinosSearch for exotic particles - Magnetic monopoles - WIMP

Selected Results

Atmospheric Muon-NeutrinosAtmospheric Muon-Neutrinos

Skyplot of NT200 neutrino events for 5 years (galactic coordinates)

372 Neutrinos in 1038 Days (1998-2003)385 events from Monte-Carlo

EETHRTHR 15-20 GeV 15-20 GeV

Lake Baikal (NT200) & South Pole ( (Amanda) Complete sky coverage including central parts of Galaxy

Lake Baikal

South Pole

Skyplot of neutrinoSkyplot of neutrinoeventsevents

Atmospheric Muon-NeutrinosAtmospheric Muon-Neutrinos

+ b + b

C + +

Limits on the excess muon flux fromLimits on the excess muon flux from the the centre of the Earth as a function ofcentre of the Earth as a function of WIMP WIMP massmass

Search of nearly vertically Search of nearly vertically upward going muons, upward going muons, exceeding the flux of exceeding the flux of atmospheric neutrino atmospheric neutrino

produced muonsproduced muons

WIMP Search

Baikal Amanda SK Baksan MACRO

T, days 1038 422 1680 5402 1298

Search for fast monopoles

N= n2 (g/e)2 N =8300 N (g = 137/2, n = 1.33) ~E=107 GeV

Event selection criteria: 1.Hit channel multiplicity Nhi t> 35 ch 2. Upward-going monopole (zi-z)(ti-t)/(tz) > 0.45 & o

Background - atmospheric muons

Limit on a flux of relativistic monopoles:

< 4.6 10-17 cm-2 sec-1 sr-1 90% C.L. upper limit on the flux of fast monopole (994 livedays)

Amanda II(preliminary)

NT200

large effective volume

NT200 is used to watch the volume

below for cascades.

(„BG“)

Search for extraterrestrial high energy neutrinos

Look for upward moving light fronts.

Signal: Bright isolated cascades from neutrino interactions

Background :Bremsshowers fromh.e. downward muons

Experimental limits + bounds/ predictions

Diffuse Neutrino Flux Limits + ModelsDiffuse Neutrino Flux Limits + Models

NT200 (1038 days)no statistically significant

excess above the background from atmospheric muons has

been observed

The 90% C.L. “all flavour” limit (1038 days) for a =2 spectrum

Ф ~ E-2 (20 TeV < E < 50 PeV), and assuming e:: = 1 1 1at Earth ( 1 2 0 at source )

E2 Ф <8.1·10-7 GeV cm-2 s-1 sr-

1 (Baikal 2006)

Searching for diffuse neutrinos based on cascades reconstruction

Energy distribution of experimental (1999),as well as generated and reconstructed events from atmospheric muons

Cascade reconstruction: lgE ~ 10%; r ~ (5-10)%; o

Selection conditions: E>100 TeV, Nhit >18

Cut E>100 TeV

old cut

Hit channel multiplicity

Expected limit (1038 days) for E-2 spectrum: E-2 ~ 4 ·10-7 GeV cm-2 s-1 sr-1 (twice lower than old one)

Antares

NT200+/Baikal-GVD

NemoNestor

KM3NeT

Amanda/IceCube/IceCube

• Deployment simplicity : ice is natural deployment platform

•Small background (bioluminescence)

• Good water properties: Scatt. Length ~ 30-60 m Abs. Length: ~25 m

Ultimate goal of Baikal Neutrino Project: Gigaton (km3) Volume Detector in Lake Baikal

Gigaton Volume Detector in Lake Baikal

Sparse instrumentation:

91 – 100 strings with 12 – 16 OMs (1300 – 1700 OMs)

- effective volume for >100 TeV cascades: ~ 0.5 -1.0 km³lgE) ~ 0.1, med< 5o

- detects muons with energy > 10 - 30TeV

624m

280m

70m

70m120m

208m

NT200+ (2005)

36 additional PMTs on 3 far ‘strings‘ 4 times better sensitivity

Improve cascade reconstruction Vgeom ~ 4 ·106 m3

Eff. shower volume: 104 TeV ~ 10 MtonExpected -sensitivity (3 yrs NT200+) E2 ФV < 2 · 10-7 GeV cm-2 s-1 sr-1

Basic building block of Basic building block of Gigaton Volume Detector Gigaton Volume Detector

NT200+ = NT200 + 3 NT200+ = NT200 + 3 outer stringsouter strings

Detection system NT200+ is the same as NT200Detection system NT200+ is the same as NT200

Prototype string km3-scale BAIKAL telescopeNT200+

current statusPrototype

stringInstallation of a “new

technology”prototype string as a part

of NT200+

Investigations and in-situ tests of basic elements of km3 detector: new optical modules, DAQ system, cable communications.

Studies of basic DAQ/Triggering approach for the km3-detector.

Confrontation of classical TDC/ADC approach with FADC readout.

60

m

Basic string elementsBasic string elements

(1) FADC sphere: 8-channel 12-bit 200 MHz FADC + Ethernet controller.(2) String PC unit: Data transmission and OMs control (3) LED Flasher unit: OM time and amplitude calibration

6 optical modules: 4 x PM XP1807 (Photonis). 2 x PM R8055 (Hamamatsu)

12

3

String control center

Optical Module (OM)

FADC unitFADC unit

Analog outputs of all 6 PMs are connected through coaxial cables with 8-channel 12 bit 200 MHz FADC board, located in the FADC unit. (two FADC channels are used to measure low-gain channels of two upper PMs)

OM power supply (12V) is provided through the analog cables (with possibility to switch on/off each individual module).

String trigger is formed by the FADC controller: 1….4-fold majority trigger within coincidence window 10ns … 1 us.

12

3

String PC unitString PC unit

Data from the FADC are transmitted through an Ethernet line to the underwater micro-PC for on-line analysis and data-compressing.

Communication between PC-unit and underwater control center of NT200+ is provided by DSL modems trough 2-wire line about 1 km length (twisted pair, now @ 2Mbps).

OM slow control and monitoring and LED flasher operation is provided by PC unit through RS-485 underwater bus. The main slow control functions are the regulation of PM high voltage, the control of LED flasher intensity and pulse delay, and the measurement of the PMT rates.

12

3

LED FlasherLED Flasher

Time and amplitude calibration is provided by the string LED flasher unit.

Light pulses from flasher are transmitted to each OM through plastic optical fibers with calibrated length.

The LED flasher provides all relative time shifts, and allows to monitor the single electron spectrum of all PMs.

The LED flasher glass sphere also houses the low noise DC-DC converters for the OM power supply .DC-DC noise amplitude ~3 mV << A(1 p.e.)LED flasher parameters:

- 2 independent LED - Pulse FWHM ~ 5 ns - Pulse delay between LED1/2 from 0…1000 ns (10 steps) - Pulse amplitude can be set from 1 to 200…1000 p.e. on PMs (~104

steps).

12

3

Optical Module (OM)Optical Module (OM)1. PMT: XP1807 (Photonis, ~12”) R8055 (Hamamatsu, ~13”) Divider 17 MOhm Gain 3...5 x 107

2. Preamplifier: Ka ~ 5 for high gain ch.

Ka ~1.5 for low gain ch.

3. HV unit: PHV12-2.0K DC-DC converter

VIP-2A (Irkutsk) converter

4. OM controller: microcontroller C8051F124 - RS-485 interface - PM pulse counter with regulated threshold - HV monitor - 2-LED calibration system (LED amplitude and pulse delay regulation, like in LED Flasher Unit).

Basic parameters ofBasic parameters of prototype string prototype string

Number of optical modules: 6

Number of spectrometrical channels: 8

Type of PMT: XP1807 (12”), R8055 (13”)

Dynamic range: high gain chan. 0.2 … ~100 p.e (*) low gain chan. 0.5 … ~300 p.e.

Time window: 5 mks

Time resolution: < 3 ns

(*) – range of spectrometrical channel linearity

Prototype string installation (April Prototype string installation (April 2008)2008)

First experience of the string installation: duration of string

deployment ~5 hours including transportation from the shore

center

Prototype string in-situ testsPrototype string in-situ tests(LED flasher)(LED flasher)

Time shift estimation with LED flasher: time difference between

neighbored OMs

OM#1

OM#2

OM#3

OM#4

OM#5

OM#6

3

2

1

4

6

5

~20 m coax cable ~20 m

A, V Example of LED flasher

event

PRELIMINARY

~20 m coax cable ~20 m

Prototype string in-situ testsPrototype string in-situ tests(Laser event)(Laser event)

OM#1

OM#2

OM#3

OM#4

OM#5

OM#6

50 m

LASER

Example of laser event with time shift correction

2

1

3

6 5

4

PRELIMINARY

Prototype string in-situ testsPrototype string in-situ tests(muon events)(muon events)

Examples of down-going muon eventsTrigger: 3-fold coincidence

1 ch Event 2 Event 3 Event 4 Event 5 Event 6

Time (nsec)2 2502 2002 1502 1002 0502 0001 950

Am

plitu

de

(V

).

0.02

0

-0.02

-0.04

-0.06

-0.08

-0.1

-0.12

-0.14

-0.16

21

3

654

PRELIMINARY

1 ch Event 2 Event 3 Event 4 Event 5 Event 6

Time (nsec).2 3002 2002 1002 0001 900

Am

plit

ud

e (

Co

de

FA

DC

).

0-100-200-300-400-500-600-700-800-900

-1 000-1 100-1 200-1 300

1 ch 6 ch Event 2 Event 3 Event 4 Event 5 Event 6

Time (nsec).2 3002 2502 2002 1502 1002 0502 000

Am

plit

ud

e (

Co

de

FA

DC

).

50

0

-50

-100

-150

-200

-250

-300

-350

-400

-450

-500

OM#1

OM#2

OM#3

OM#4

OM#5

OM#6

CONCLUSIONCONCLUSION

1. 1. BAIKAL lake experiment is BAIKAL lake experiment is successfully running since 1993 - The First Underwater Array - First Neutrino Candidates - Some HE neutrino production models already ruled out by the experiments

2. NEW configuration NT200+ starts work at April 2005 and is successfully operating now. - Improved cascade reconstruction - NT200+ gives good possibilities to optimise the design and to investigate the key elements of future Gton scale detector

3. Start R&D for Gigaton Volume (km3-scale) Detector (BAIKAL-GVD) - A “new technology” prototype string was installed: 6 OMs with 12”/13” - Preliminary in-situ tests of the prototype string with underwater laser, LED flasher and muons shows good performance of all string elements.

ENDEND

3 ch

Time (nsec)3 2003 0002 8002 6002 4002 200

Am

plit

ud

e (

V).

0,6

0,4

0,2

0

-0,2

-0,4

-0,6

-0,8

-1

-1,2

-1,4

-1,6

Estimation of the string Estimation of the string time resolution (LED time resolution (LED

events)events)

LED1 LED2

LED pulse fits (time estimation) LED1-LED2 delay distribution

Ch# LED1-LED2 delayestimation, ns

RMS, ns

2 497.45 1.40

3 497.15 0.80

5 496.75 2.80

6 497.00 2.65

7 497.20 1.05

PRELIMINARY

<Time resolution> ~1.5 ns in the range 5…100 p.e.