STATUS OF BAIKAL NEUTRINO EXPERIMENT: Vladimir Aynutdinov, INR RAS, Moscow for the Baikal Collaboration for the Baikal Collaboration HECR’ May 2008

Collaboration  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.

Baikal Outline: Introduction Neutrino telescope NT200 ( ) Design and Physics Results (selected) Future Gigaton-Volume (km3-scale) detector BAIKAL-GVD Preliminary Design NT200 upgrade  NT200+ ( ) 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 NT NT36 started (36 PMTs at 3 strings) The First Underwater Array First Neutrino Candidates NT200 commissioned NT200 commissioned Start full Physics program NT200+ commissioned /6 NT200+ commissioned /7 R&D for Gigaton (km3-scale) Volume Detector (GVD) 2008 April prototype string for GVD was installed2008 April prototype string for GVD was installed

The Site 4 cables x 4km to shore. 1070m depth 3600 m 1366 m NT-200 Absorption length: ~25m Scattering length: m Detection volume >> geometrical volume

Ice stable for 6-8 weeks/year: –Maintenance & upgrades –Test & installation of new equipment Winches used for deployment

-8 strings: 192 optical modules  96 measuring channels  T, Q measure *Timing ~ 1 nsec *Dyn. Range ~ 10 3 ph.e. Effective area: 1 TeV~2000m² Eff. shower volume: 10TeV~ 0.2Mt Quasar : d = 37cm Height x  = 70m x 40m, V inst =10 5 m 3

Low energy phenomena (muons) - Atmospheric neutrinos High energy phenomena (cascades) Diffuse neutrino flux - Diffuse neutrino flux - Neutrinos from GRB - Prompt muons and neutrinos Search for exotic particles - Magnetic monopoles - WIMP Selected Results

Atmospheric Muon-Neutrinos Skyplot of NT200 neutrino events for 5 years (galactic coordinates) 372 Neutrinos in 1038 Days ( ) 385 events from Monte-Carlo E THR GeV

( Lake Baikal (NT200) & South Pole (Amanda) Complete sky coverage including central parts of Galaxy Lake Baikal South Pole Skyplot of neutrino events Atmospheric Muon-Neutrinos

 +   b + b C +  +  Limits on the excess muon flux from the centre of the Earth as a function of WIMP mass Search of nearly vertically upward going muons, exceeding the flux of atmospheric neutrino produced muons WIMP Search

Search for fast monopoles N   = n 2 (g/e) 2 N   =8300 N   (g = 137/2, n = 1.33) ~E  =10 7 GeV Event selection criteria: 1.Hit channel multiplicity N hi t > 35 ch 2. Upward-going monopole  (z i -z)(t i -t)/(  t  z ) > 0.45 &  o Background - atmospheric muons Limit on a flux of relativistic monopoles:  < 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 from h.e. downward muons

Experimental limits + bounds/ predictions Diffuse 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  1 at Earth ( 1  2  0 at source ) E 2 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, N hit >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 Nemo Nestor KM3NeT /IceCube Amanda/IceCube Deployment simplicity : ice is natural deployment platform Small background (bioluminescence) Good water properties: Scatt. Length ~ 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: ~ km³  lg  E) ~ 0.1,  med  < 5 o - detects muons with energy > TeV 624 m 280m 70m 120m 208m

NT200+ (2005) 36 additional PMTs on 3 far ‘strings‘  4 times better sensitivity  Improve cascade reconstruction Vgeom ~ 4 ·10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton Expected -sensitivity (3 yrs NT200+) E 2 Ф V < 2 · GeV cm -2 s -1 sr -1 Basic building block of Gigaton Volume Detector NT200+ = NT outer strings Detection system NT200+ is the same as NT200

Prototype string km3-scale BAIKAL telescope NT200+ current status Prototype string Installation 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 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) String control center Optical Module (OM)

FADC 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

String 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, 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

LED 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 (~10 4 steps)

Optical Module (OM) 1.PMT: XP1807 (Photonis, ~12”) R8055 (Hamamatsu, ~13”) Divider 17 MOhm Gain x Preamplifier: K a ~ 5 for high gain ch. K a ~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 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 2008) First experience of the string installation: duration of string deployment ~5 hours including transportation from the shore center

Prototype string in-situ tests (LED flasher) Time shift estimation with LED flasher: time difference between neighbored OMs OM#1 OM#2 OM#3 OM#4 OM#5 OM# ~20 m coax cable ~20 m A, V Example of LED flasher event PRELIMINARY ~20 m coax cable ~20 m

Prototype string in-situ tests (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 PRELIMINARY

Prototype string in-situ tests (muon events) Examples of down-going muon events Trigger: 3-fold coincidence PRELIMINARY OM#1 OM#2 OM#3 OM#4 OM#5 OM#6

CONCLUSION 1. BAIKAL lake experiment is 1. BAIKAL lake experiment is successfully running since 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.

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Estimation of the string time resolution (LED events) LED1 LED2 LED pulse fits (time estimation)LED1-LED2 delay distribution Ch# LED1-LED2 delay estimation, ns RMS, ns PRELIMINARY ~1.5 ns in the range 5…100 p.e.