Lake Baikal: from Megaton to Gigaton. Bair Shaybonov, JINR, Dubna on behalf of the Baikal Collaboration

Transcription

1 Lake Baikal: from Megaton to Gigaton Bair Shaybonov, JINR, Dubna on behalf of the Baikal Collaboration TAUP09, Rome, July 2009

2 Outline Status of the Baikal Detector Selected Results obtained from NT200 array data Activity towards Gigaton Volume (km 3 scale) Detector Summary 2

3 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

4 Present Status NT200 array: 192 Optical Modules 8 Strings 6.5 m between Modules 20 m between strings NT+ array: 36 Optical Modules 3 distant Strings New technology string: 12 Optical Modules 10 m between Modules All parts work in joint regime 4

5 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 > 2006 Upgrade to NT200+ completed and is operating R&D activity for a Gigaton Volume Detector in Lake Baikal 2011 Start of GVD cluster prototype 5

6 The Site NT200+ deployment from 1m thick ice, 4km off-shore. NT+ String 1 Cable Station NT+ String 3 NT200 Strings NT+ String 2 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. 6

7 Cable Laying on the Lake Bed Relatively simple laying technique, because of: Stable ice cover Close to shore (3.6 km) cable tractor with ice cutter ice slot cable layer Separate cable string (station). Connections are done on dry 7

8 Deep Water Optical Properties Baikal Baikal Abs.Length: 22 ± 2 m, nm, nm Scat.Length: m <cosθ>: No high luminosity bursts from biology 8

9 NT200 Array strings optical modules = 96 pairs (coincidence) - Time + Charge measured - σ T ~ 1 ns - dyn. range ~ 1000 p.e. Effective area: 1 TeV ~ 2000 m² Eff. Shower volume: 10 TeV ~ 0.2 Mton 1 PeV ~ 1Mton Height = 70m, = 42m V inst = 0.1 Mton Quasar PMT: 37cm (14.6 ), hybrid, mushroom shape 9

10 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 NEW NEW NEW Data Sample: (Apr98 Feb03) = 1038 live days NT200+ data analysis is ongoing 10

11 Diffuse Flux Limits New analysis of existing data with vertex, energy and direction reconstruction of cascades: improvement of published limit by a factor of ~ 3! The 90% C.L. all flavour limit, e : : = (20 TeV < E < 20 PeV) E 2 Ф n < GeV cm -2 s -1 sr -1 (Cascades Baikal, 2008) E 2 Ф n < GeV cm -2 s -1 sr -1 (Muons AMANDA-II, 2007) E 2 Φ(E), GeV cm -2 s -1 sr -1 Model Model rejection factor n 90% /N model BAIKAL AMANDA Stecker (05) Mannheim (95) pp+pγ Protheroe (96) pγ Mannheim,Protheroe, Rachen (01) Semikoz,Sigl (03)

12 WIMP Neutrinos from the Sun - 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 Sun-mismatch angle Ψ (Muon/Sun): data and background (histogram) Baikal NT200: , hard AMANDA-II 2001, hard Baksan 1997 MACRO 1998 Super-K 2001 No excess of events above atm. ν BG Flux Limits IceCube , hard 12

13 GRB Neutrino Search Search for direction + time correlations with 303 GRBs observed by BATSE in , using the upward-going muon data sample. Time window: (t GRB + T s) - (t GRB -5s) Half angle of observation cone: Ψ = 5 o Green s function Upper Limits on GRB neutrino fluence (model independent) Observed number of events 1 event Expected number of bg. events 2.7 events SK Amanda-II Baikal NT200 F(E ν ) = N 90% / S eff (E ν ) N 90% - 90% C.L. upper limit on the number of events per GRB 13

14 Acoustic Studies since m depth Average noise 2.5 mpa navigation wind Acoustic module allows: develop technique of acoustic registration acoustic noise monitoring Hydrophones: mv/pa khz Most of bipolar impulses come from lake surface θ Small noise level would compensate small signal amplitude Further activity is needed New string R&D design 2011 Tests with acoustic string prototype, first data 14

15 Z ~ m m String section Gigaton Volume Detector in Lake Baikal Top view 12 clusters each 8 strings = 96 strings with OMs = OMs total MC parameters optimization is in progress: H ~ m R ~ m Z ~ m Cluster of strings 15

16 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 completed in 2005 NT200+ data analysis is ongoing 16

17 Laser pulses as HE cascades Laser intensity Cascade energy γ/pulse ~ PeV RMS = 2-3 ns Laser reconstruction accuracy: Position better 1 m Intensity 6 % 17

18 GVD Performance (very preliminary estimations) HE cascades effective volume HE muons effective area V eff 0.25 km 3 for 100 TeV A eff 0.20 km 2 for 10 TeV Trig. 4/3. min. 2 fired ch. in 1 string Cascades detection with E > 100 TeV: dlg(e) ~ 0.1, dψ med < 4 o Muon detection with E > 10 TeV: dψ med ~ 0.5 o Trig. 5/3 r60_z15_h250 18

19 In-situ test of the Prototype String Section 2009 New Optical Module, DAQ development since 2006 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: Time window: 5 µs Time resolution: Calibration system: 0.2 ~100 p.e. 3 ns LED Matrix for Time calibration Two LEDs on each OM for amplitude calibration External laser source for synchronization with other strings PMT 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. LEDs Comparison of the classical TDC/ADC approach with a FADC-based full pulse shape readout. 19

20 Amplitude [codes] Time accuracy of the String Section OM #1 Wave forms example OM #10 OM #1 OM #9 OM #10 Time diff. OM #9 and OM #10 Laser: nearly isotrope light source Data processing and analysis are ongoing Preliminary in-situ tests with underwater laser, LED flasher and muons show good performance of all string elements FWHM = 3ns 20

21 Schedule GVD R&D (supported by Russian foundation) GVD Technical Design Project GVD Cluster Prototype Fabrication (OMs, electronics, cables, etc) Deployment km Deployment km Deployment km 3 21

22 Summary 1. Lake Baikal Experiment has been successfully running since 1993 the first underwater array and first neutrino candidates 2. NT200+ Array is working since 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

23 Ice camp view from shore. April 2009 Thank You 23