Gigaton Volume Detector in Lake Baikal Vladimir Aynutdinov for the Baikal Collaboration Cassis, May 3, th International Workshop on Ring Imaging Cherenkov Detectors (RICH 2010) RICH Cassis, Provence, France, 3-7 May 2010

1. Institute for Nuclear Research, Moscow, Russia. 2. Irkutsk State University, Russia. 3. Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia. 4. DESY-Zeuthen, Zeuthen, Germany. 5. Joint Institute for Nuclear Research, Dubna, Russia. 6. Nizhny Novgorod State Technical University, Russia. 7. St.Petersburg State Marine University, Russia. 8. Kurchatov Institute, Moscow, Russia.

Introduction Baikal Neutrino Experiment - Overview Baikal – Milestones The Baikal site NT200+ present status Future Gigaton-Volume Detector in Baikal lake (BAIKAL-GVD ) The physics with BAIKAL-GVD BAIKAL-GVD technical design BAIKAL-GVD prototype strings Summary

Since 1980 Site tests and early R&D started 1990 Technical Design Report NT NT NT36 started: - the first underwater array - the first neutrino events NT200 commissioned: 1998 NT200 commissioned: start full physics program. NT200+ commissioned (NT200 & 3 outer strings) NT200+ commissioned (NT200 & 3 outer strings) Start R&D for Gigaton Volume Detector (GVD) 2008 In-situ test GVD electronics: 6 new technology optical modules 2008 In-situ test GVD electronics: 6 new technology optical modules Prototype strings for GVD In-situ tests PMT XP1807, R8055, R7081HQ In-situ tests PMT XP1807, R8055, R7081HQ 2011 GVD cluster (3 strings), Technical Design Report 2011 GVD cluster (3 strings), Technical Design Report

5 Baikal, nm Absorption cross section, m -1 Scattering cross section, m -1 ice slot cable tractor with ice cutter cable layer Shore cable mounting Deployment with winches Distance to shore 4 … 5 km 1370 m maximum depth Deployment simplicity (ice as a deployment platform) Abs.Length: 22 ± 2 m Scat.Length: m No high luminosity bursts from biology The BAIKAL Site Water properties Lake Baikal, Siberia

NT200: 8 strings (192 optical modules ) Height x  = 70m x 40m, V inst =10 5 m 3 Effective area: 1 TeV~2000m² Eff. shower volume: 10 TeV~ 0.2 Mton Quasar photodetector (  =37cm) NT200+ = NT outer stringw (36 optical modules) Height x  = 210m x 200m, V inst = 4  10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton Status of NT200+ LAKE BAIKAL ~ 3.6 km to shore, 1070 m depth NT200+ is operating now in Baikal lake

A NT200+/Baikal-GVD (~2017) N N KM3NeT (~2017) /IceCube Amanda/IceCube(~2011) ANTARES 79 Strings in operation

The Physics with BAIKAL-GVD

1. Point sources / atmospheric neutrinos ( E v > 10 TeV ) Skyplot of NT200 neutrino events (galactic coordinates) 372 Neutrinos in 1038 Days ( ) 385 events from Monte-Carlo A search for up-going muon ( δθ med ~ 0.3 o -0.5 o ), and cascades ( δθ med ~ 3 o - 6 o ) All-sky search or pre-defined sources (supernova remnants, pulsars and micro-quasars, extragalactic sources: AGN and GRB emitters); search for events from galactic center (Sgr A * ). E THR GeV NT200

2. Diffuse High Energy Neutrinos The 90% C.L. “all flavor ” limit, e :  :  =1  1  1 Cut E>10 TeV for up-going cascades Cut E>100 TeV for down-going cascades E 2 Ф n < 2.9 ·10 -7 GeV cm -2 s -1 sr -1 Energy distribution of experimental (red), generated (blue) and reconstructed (black) events from atmospheric muons. NT200 Studies of bright cascades detected in the telescope: a search for excess above the expected background from atmospheric muons. A search for local anisotropy.

Search for up-going muons correlated with GRB in time and direction. Information about GRB time and location on the sky allows reducing the atmospheric muon background. 3. Transient sources (e.g. GRBs) For Waxman – Bahcall spectrum and triggered bursts (155 GRB) E 2   1.1×10 -6 GeVcm -2 s -1 sr -1, E >100 TeV April May % C.L. upper limits on the GRB neutrino fluence Green's function for NT200, Super- Kamiokande and AMANDA F(E v )=N 90 / S eff (E v ) NT200

4. Neutrinos from DM annihilations Limits on the excess muon flux from the Sun as a function of WIMP mass Limits on the excess muon flux from the Sun as a function of WIMP mass (1007 live days of NT200) Baikal NT200: , hard Baksan’199 7 AMANDA-II’2001, hard MACRO’199 8 Super- K’2001 IceCube-22’2007, hard Preliminary NT200 A search for possible signal from WIMP annihilation in the centres of the Earth, the Sun, the Galaxy (“indirect” WIMP search). An analysis of excess of up-going muons over atmospheric neutrinos arriving from the given direction.

5. Exotic physics Limit on a flux of relativistic magnetic monopoles (1003 days of live time): F < cm -2 sec -1 sr -1 90% C.L. upper limit on the flux of fast monopole Amanda II NT200 Fast monopoles: a search for long bright tracks with uniform light emission and upward moving light patterns. (for a Dirac charge g = 68.5 e, Cerenkov radiation emitted by monopoles is 8300 times more that of a muon) Fast and slow monopoles

BAIKAL-GVD Technical design

Optimisation of GVD configuration (preliminary) Cascade detection volume Parameters for optimization: Z – vertical distance between OM R – distances between strings and cluster centre H – distances between cluster centres Muon effective area R=80 m R=100 m R=60 m The compromise between cascade detection volume and muon effective area: H=300 m R = 60 m Z = 15 m Trigger: coincidences of any nearby OM on string (thresholds 0.5&3p.e.) PMT: R7081HQE,10”, QE~0.35

16` Cluster of strings String section, 12 OM R ~ 60 m L~ 350 m 15 m Layout: ~2300 Optical Modules at 96 Strings String: 24 OM  2 Sections with 12 OM Strings are combined in Clusters  8 strings Cascades (E>100 TeV): V eff ~0.3–0.8 km 3 δ (lgE) ~0.1, δθ med ~ 3 o - 6 o Muons (E>10 TeV): S eff ~ 0.1 – 0.7 km 2 δθ med ~ 0.3 o -0.5 o Preliminary design 12 clusters of strings NT1000: top view

Cable communication to shore 1370 m maximum depth Distance to shore 4 … 5 km 12 clusters × 192 OM 12 cables ~ 6 km GVD cluster 12 Shore cables ~6 km 1350…1370 m Shore Center 12 GVD clusters NT200+

Cluster DAQ center Cluster of strings 8 Strings String consists of 2 sections (2×12 OM) Cluster DAQ Centre (4 modules) 1. PC-module with optical Ethernet communication to shore (data transmission and synchronization) 2. Trigger module with 8 FADC channels (time mark of string trigger) 3. Data communication module (8 DSL-modems for communication to strings, ~10 Mbit/s for 1 km ) 4. Power control system

Section – basic detection unit Section: - 12 Optical Modules - BEG with 12 FADC channels and trigger unit - Service Module (SM): LEDs for OM calibration, OM power supply, acoustic positioning system. Basic trigger: coincidences of nearby OM (threch. ~0.5&3 p.e.) expected count rate < 100 Hz Communications: BEG  cluster centre: DSL-modem, expected dataflow < 1Mbit/s BEG  OMs: RS-485 Bus (slow control)

Optical module XP1807(12”), R8055(13”) ‏, R7081HQE(10”) QE ~0.24 QE ~0.2 QE~0.35 HV unit: SHV12-2.0K,TracoPower OM controller Amplifier: K amp = 10 LED calibration system (2 LEDs) Functional scheme of the optical module electronics XP1807 R8055 R7081 HQE Relative sensitivities of large area PMs R8055/13” and XP1807/12”

Measuring channels BEG PMT 1 AmplifierFADC 1 90 m coax.cable OM PMT 12 AmplifierFADC m coax. cable … BEG (FADC Unit) -3 FADC-board: 4-channel, 12 bit, 200 MHz; -OM power controller; -VME controller: trigger logic, data readout from FADC, connection via local Ethernet

BAIKAL-GVD prototype strings

In-situ tests of basic elements of GVD with prototypes strings ( ) Investigation and tests of new optical modules, DAQ system, cabling system, triggering approaches ( LED Laser Muons) NT200+ Prototype string 2009 Prototype string 2010 PMT: Photonis XP OM Hamamatsu R OM PMT: Hamamatsu R7081HQE 7 OM Hamamatsu R OM GVD prototype strings

R7081HQE R8055 Prototype string deployment: April 2010 PC BEG1 SM BEG2

Time resolution of measuring channels (in-situ tests with LED) LED flasher produces pairs of delayed pulses. Light pulses are transmitted to each optical module (channel) via individual optical fibers. Delay values are calculated from the FADC data. Measured delay dT between two LED pulses LED1 and LED 2 pulse amplitude Example of a two-pulse LED flasher event (channel #5) LED1 LED2  (dT) 1.6 ns

Time accuracy (in-situ test with Laser) LASER 110 m OM#7 OM#8 OM#9 OM#10 OM#11 OM#12 OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 97 m r1r1 r2r2 Differences between dT measured with Laser and expected dT in dependence on distances between channels dr  T < 3 ns Test with LASER  T = dT EXPECTED = (r 2 -r 1 )  c water dT LASER - time difference between two channels measured for Laser pulses (averaged on all channel combinations with fixed (r 2 -r 1 ))

Distribution of time difference  T between muon pulses for two up-ward looking PMTs: experiment and calculation.  T between muon pulses detected with different channels are studied and compared with simulation of the string response to the atmospheric muon flux. Trigger: 3-fold OM coincidences Muon detection

Summary 1.The Baikal neutrino telescope NT200 is working successfully for more than 10 years. - The First Underwater Array - First Neutrino Candidates 2. Preparation towards a km 3 -scale Gigaton Volume Detector in Lake Baikal is currently a central activity. - A “new technology” prototype strings were installed: 12 OMs with PMT R8055 and XP1807 (2009); 10 OMs with PMT R7081HQE and R8055 (2010). - In-situ tests of the prototype string with underwater LED flasher, Laser, and muons shows good performance of all string elements. - GVD Technical Design Report is expected at 2011