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Physics Laboratory

Physics Laboratory. School of Science and Technology. Hellenic Open University. Use of fl oating surface detector stations for the calibration of a deep-sea neutrino telescope. G. Bourlis , N. A. B. Gizani , A. Leisos , A. G. Tsirigotis , S.E. Tzamarias.

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Physics Laboratory

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  1. Physics Laboratory School of Science and Technology Hellenic Open University Use of floating surface detector stations forthe calibration of a deep-sea neutrinotelescope G. Bourlis, N. A. B. Gizani, A. Leisos, A. G. Tsirigotis, S.E. Tzamarias In the framework of the KM3NeT Design Study

  2. Use of EAS detector stations forthe calibration of KM3NeT The General Idea… • Angular offset • Efficiency • Resolution • Position Physics ? C.R. composition UHE ν - Horizontal Showers Veto atmospheric background – Study background

  3. Isotropic on the top of the atmosphere BUT … α~10 Range of muon in water ~4km ~20km

  4. EAS Calibration Method - The Concept A floating array of EAS detectors can be used as a sea-topcalibration infrastructure, on top of the KM3NeT neutrino telescope. Such anarray can detect atmospheric showers and the collected data can be used for thereconstruction of the direction and the estimation of the impact parameter of the shower axis. Cosmicshowers with energiesabove 1014eV contain energetic muons able topenetrate the 4000m deep sea water and reach the KM3NeT detector. Thecomparison of the reconstructed muontrack parameters with the estimated shower axis: Floating stations Atmospheric Muon • Revealsany possible systematic angular error of the neutrino telescope and, • Providesthe absoluteposition of the undersea detector. Underwater Neutrino Telescope

  5. The SeaTop Detector – HELYCON Station • The EAS array used in this study consists of floating HELYCON (HEllenic LYceum Cosmic Observatories Network) scintillation counters. • Each HELYCON stationincludesa GPS antenna,digitization and controlelectronics and the data acquisition system controlled by a PC. • A single station is able to detectatmospheric showers initiatedby cosmic particles of energy more than 1014–1015 eV. • The reconstruction of the shower axis is based on the measurement of: • a) the arrival times and • b) the amplitude of the detector signals. Scintillator-PMT GPS Triangulation Shower Direction 1 m2 ~20 m Station Server DAQ

  6. The EAS Charged Particle Detector - DAQ • 1 m2active area scintillation counter. • The ReadOut system is based on aHPTDC chip, designed at CERN,with 5 analogue inputs. • The input signals are compared to sixadjustable thresholds and the corresponding times of thePMT waveform-threshold crossings are digitized with an accuracy of 100ps. • Thesynchronization between the HELYCONstations relies on theGPS time-signal which is incorporated in the data. Scintillator 1 Station Server Scintillator 2 Scintillator 3 GPS timestamp Scintillator 4

  7. Simulation Tools to describe the detector response CORSIKA (Extensive Air Shower Simulation) • The CORSIKAairshower simulation software is used to produce air showers, initiated bycosmic ray particles entering isotropically the upper atmosphere. • Detector response, trigger formation, digitizationand the Data Acquisition System is simulated by the specific HELYCON MC package. • Theeventsproduced by the simulation are stored using thesame format as theexperimental data and they are analyzed in exactly the same way as real events. GEANT4 (Scintillation, WLS & PMT response) DAQSIM (DAQ Simulation) HOUANA (Analysis & Shower Reconstruction)

  8. Calibration and Test Results Global time resolution and slewing Slewing Scintillator A discriminators Lead Scintillator B Inputs Resolution Trigger Response to a MIP • Data -Monte Carlo Prediction Local time resolution Charge (in units of mean p.e. charge) ΔT [ns] 21 pes mean <10% variation

  9. Shower reconstruction –Timing Corrections curvature thickness Plane wave Hypothesis χ2minimization

  10. curvature Statistical Error [ns] Deposited Charge [MIP] Time corrections Arrival Time Delay [ns] Deposited Charge [MIP] thickness

  11. Observations of Extensive Air Showers - Resolution The performance of HELYCON in detecting andreconstructing showershas been studied by operatinga system of eight HELYCON detectors in thelaboratory. σ= 7.2ο±0.2ο MC Estimated resolution group A σAMC=4.5ο±0.5o , group B σBMC=5.2ο±0.6o, all six detectors σ6MC=3.5ο±0.3o. These resolutions can be evaluated solely from thereal data, by comparing the resultsobtained by the two detector groups (A andB) on an event by event basis. The distribution of the difference (Δθ=θΑ-θΒ) ofthese two estimations of the zenith angle has a spread of σDATA =7.2ο±0.2ο. This spread is consistent with the above MCpredictionsof the detector resolution:

  12. Observations of Extensive Air Showers zenith angle [degrees] zenith angle [degrees] Trigger Detectors > 1.5 mip Detectors of groups A.and.B > 1.5 mip’s Trigger Detectors >1.5 mip Detectors of groups A.and.B > 0.5 mip’s α=9.4±0.2

  13. SeaTop Detector – Station Setup Station 5m 19m 1 m2 Scintillation Counter 19m - Three Floating Stations operating independently above KM3NeT- Distance between stations 150m- 16m2 Scintillator Each Station

  14. Single Station Detection Efficiency Efficiency Events A hit is considered when there is more than 4 mips deposited charge on a counter

  15. Muon Propagation Accepted if muon with E>2TeV goes through km3 Geant Simulation (propagation & Energy Loss) μ track Zenith angle < 13 deg km3 Detector response simulation and Muon Track Reconstruction

  16. Monte Carlo Studies- Outlook1014 - 5·1015 eV E~ 1014 - 5·1015 eV: 2500 showers/m2/year Single station detection: 360m2 geometrical area (effective area depends strongly on selection cuts) E> 1016 eV: 1 shower/m2/year TO BE STUDIED 35% of the detected showers include a muon which arrives at the Neutrino Telescope (depth 4000m) with an energy >300GeV General Remark: 3 stations operating for 10 days can identify an angular offset of the KM3NeT with an accuracy of 0.05o Specifically…..

  17. Investigation for a systematic angular offset of the KM3NeT • We use EAS that contain at least one energetic muon reconstructed by the KM3NeT and compare the estimated zenith angles of the shower axis andthe muon track on an event by event basis. • The difference between these two angles should follow a normal distributionwith mean zero.A possible statistically significant deviation from zeroindicatesthat the estimations of the KM3NeT suffer from a systematicangularoffset. • The spread of thisdistribution expressesthe calibration resolution per shower event.

  18. Investigation for a systematic angular offset of the KM3NeT σ1(na) Aeff(na) [m2] na na The calibration resolutionper single shower decreases when events with more active detectors areselectedbecause the reconstruction accuracy of theshower’s direction improves. However, the requirement of more active detectorsperevent results to a reduction of the effective area of the floating detectorarray. Calibration resolution per single shower event (degrees) Effective area of a floating detector station na : minimum number of active detectors per shower event

  19. Investigation for a systematic angular offset of the KM3NeT σc(na) [degrees] na The calibration resolution, σc(na), in identifying a possible angular offset inthe neutrino telescope estimations using the three floating detector arrays, is: For 3 EAS detector stationsand 10 days of operation the calibration resolution has a minimum for na≤5 . The proposed calibrationsystem will be able to measure a possible zenith angle offsetwith an accuracy of ~0.05o. minimum number of active detectors per shower event.

  20. Charge parameterization AGASA parameterization (S. Yoshida et al., J Phys. G: Nucl. Part. Phys. 20,651 (1994) Parameters depend on (θ,Ε, primary) “Mean particle density registered by an active counter”

  21. Determination of the KM3NeT Absolute Position (a) na (b) na The resolution in estimating the (X-Y) coordinates of the under-water detector, as afunction of the number of active detectors, using: (a)single reconstructedEAS and (b) showers collected by three floating arrays during 10 days of operation. The proposed technique can estimate the absoluteposition of the neutrino telescope with an accuracy ~0.6m.

  22. Conclusions The operation of 3 stations (3x16 counters) for 10 days will provide: • The determination of a possible angular offset of the KM3NeT with an accuracy ~ 0.05 deg • The determination of the absolute position of the KM3NeT with an accuracy ~ 0.6 m • Efficiency vs Energy and Zenith angle…

  23. spase-amanda 1 km 2 km IceCube IceTop SPASE air shower arrays  calibration of AMANDA angular resolution and pointing !  resolution Amanda-B10 ~ 3.5°

  24. The Underwater Neutrino Telescope – Working Example 125m IceCube Geometry 9600 OMs looking up & down in a hexagonal grid. 80 Strings, 60 storeys each. 17m between storeys MultiPMT Optical Module 20 x 3” PMTs (Photonis XP53X2) in each 17” Optical Module

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