Status of the BAIKAL GVD neutrino project

1. Status of the BAIKALGVD neutrino project I.Belolaptikov behalf BAIKAL collaboration SINP MSU, July 7, 2012

3. Site properties Summer expedition >250 km3 Winter expedition Day temperature Depth – 1360 m with flat bedat distance> 3 km from the shore allows > 250 km3 instrumented volume !

4. Site properties • Strong ice cover during ~2 months: - Telescope installation, maintenance, upgrade and rearrangement - Installation & test of a new equipment - All connections are done on dry - Fast shore cable installation (3-4 days) • Water optical properties: - Absorption length – 22-24 m - Scattering length – 30-50 m • - Moderately low background in fresh water • Water propertiesallow detection of all flavor neutrinos with high direction-energy resolution! cable Shore cable deployment tractor with ice cutter ice slot cable layer March 2011

5. 1998 - NT200 2005 - NT200+ Quasar photodetector (=37cm) NT200: 8 strings (192 OMs) Height x  = 70m x 40m, Vinst=105m3 Effective area: 1 TeV~2000m² Eff. shower volume: 10 TeV~ 0.2 Mton NT200+ = NT200 + 3 outer strings (192+36 OMs) Height x  = 210m x 200m, Vinst = 5106m3 Eff. shower volume: 104 TeV ~ 10 Mton ~ 3.6 km to shore, 1070 m depth

6. Gigaton Volume Detector (GVD) in Lake Baikal R&D status Objectives: - km3-scale 3D-array of photodetectors - flexible structure allowing an upgrade and/or a rearrangement of the main building blocks (clusters) - high sensitivity and resolution of neutrino energy, direction and flavor content Central Physics Goals: - Investigate Galactic and extragalactic neutrino “point sources” in energy range > few TeV - Diffuse neutrino flux – energy spectrum, local and global anisotropy, flavor content - Transient sources (GRB, …) - Dark matter – indirect search - Exotic particles – monopoles, Q-balls, nuclearites, …

7. Structure elements of the detector Section OM String Cluster 12-16 OM 2-4 Sections 8 Strings To the shore L~ 705m String section, 12 OMs R ~ 60 m

8. GVD desing Configuration 10368Optical modules, 216Strings: 48OM/Str., 4 Sec./Str. 27Clusters: 8 Str/Cluster Geometry: Z = 15 m – distance between ОМ on string R = 60 m – cluster radius H = 300 m – distance between clusters Instrumented volume: ~1.5km3 Depth: 600-1300 m Muons:(E>1TeV): Seff~ 0.3–1.8 km2 ;δθmed< 0.5o ; δlg(E/Em) ~0.4 Cascades: (E>10 TeV): Veff~0.4–2.4 km3; δ(E/Esh) ~25%; δθmed~ 5o 10368 OMs 10368 OMs 2304 OMs 2304 OMs

9. GVD prototype strings 2009 - 2010 Prototype string 2009 Prototype string 2010 PMT: Photonis XP1807 6 OM Hamamatsu R8055 6 OM PMT: Hamamatsu R7081HQE 7 OM Hamamatsu R8055 3 OM NT200+ In-situ tests of basic elements of GVD with prototypes strings (2009...2010) Investigation and tests of new optical modules, DAQ system, cabling system, triggering approaches ( LED Laser Muons)

10. Prototype string: muon reconstruction Noise suppression procedure: The time difference between the pulses of any pair of OMs should be smaller than the light propagation time. • - Performance of time measuring systems. • - Reliability of calibration methods. • Efficiency of background suppression. Selected sample of 2010 string data: - Trigger condition: >3 hit OMs - PMT noise: ~15kHz Muon track reconstruction: Zenith angular distributions of experimental and MC-simulated events after cuts

11. Cluster 2011 technical design • Optical modules • The OMs house photomultipliers of different types: • 16 PMT R7081HQE (Hamamatsu, 10 inch) • 5 PMT R8055 (Hamamatsu, 13 inch) • 3 PMT XP1807 (Photonis, 12 inch • Strings • Size reduced section:8 optical modules, CM and SM. • CM (Central module): 2ADC board (8 chan.), Master . • SM (Service module): Control and connection to the • cluster DAQ center. • Acoustic positioning system, 3 modules on each string. (accuracy ~2 cm, measurements each 30 sec) • Cluster DAQ center • Cluster DAQ center provides the string triggering, power supply, and communication to shore. • Communication lines • Connection between the strings and cluster DAQ center: 1.2 km copper cable. Connection to shore – optical cable 6 km.

12. BAIKAL-GVD prototype cluster: 2011 NT200+ communication lines Optical cable 2011 248 “live” days NT200+ • In April 2011, a prototype cluster of GVD was installed in Lake Baikal. • 3 vertical strings with 8 optical modules each. • Vertical spacing between OMs is 10 m. • Horizontal distance between strings is 40 m. • Depths is 1205 – 1275 m. Sketch of prototype cluster, neutrino telescope NT200+, and communication lines locations.

13. Present and nearest future 2012 3-strings, firstfull scale GVD string (24ОМ) Data taking since April 2012 2013 Detector with 3 full scale GVD strings 2014-2015 Cluster(8 strings) DAQ DAQ DAQ DAQ DAQ DAQ 106 м3 4106 м3

14. Plans • Preproduction: • 2014–2015. Full scale GVD cluster, 8 strings (192 Oms) • Production (preliminary) • 2014–2018:12-14 Clusters • 2018–2020: Full scale detector ( 27 clusters )

15. Summary 1. Preparation towards a km3-scale Gigaton Volume Detector in Lake Baikal is currently a central activity: - In-situ tests of the prototype string shows good performance of basic string elements (2009-2010). - A prototype GVD cluster with 3 strings was installed (2011) and shows stable work for whole year. - New technology underwater optical cable was mounted (2011). - Full scale GVD string(24 OMs) with 2 “short” strings(6 OM) taking data since April 2012. 2. Full scale GVD cluster (~200 OMs) is expected at 2014-2015. GVD Technical Design Report was prepared (2011): http://baikalweb.jinr.ru/GVD/

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