Use of floating surface detector stations for the calibration of a deep-sea neutrino telescopeG. Bourlis, N. A. B. Gizani, A. Leisos, A. G. Tsirigotis, S.E. TzamariasIn the framework of the KM3NeT Design Study

The General IdeaAngular offsetEfficiencyResolutionPositionPhysics ?C.R. compositionUHE - Horizontal ShowersVeto atmospheric background Study backgroundUse of EAS detector stations for the calibration of KM3NeT

~4km~20kmIsotropic on the top of the atmosphere BUT ~10Range of muon in water

EAS Calibration Method - The ConceptFloating stationsA floating array of EAS detectors can be used as a sea-top calibration infrastructure, on top of the KM3NeT neutrino telescope. Such an array can detect atmospheric showers and the collected data can be used for the reconstruction of the direction and the estimation of the impact parameter of the shower axis. Cosmic showers with energies above 1014 eV contain energetic muons able to penetrate the 4000m deep sea water and reach the KM3NeT detector. The comparison of the reconstructed muon track parameters with the estimated shower axis:Atmospheric MuonUnderwater Neutrino TelescopeReveals any possible systematic angular error of the neutrino telescope and, Provides the absolute position of the undersea detector.

The SeaTop Detector HELYCON StationTriangulation Shower DirectionThe EAS array used in this study consists of floating HELYCON (HEllenic LYceum Cosmic Observatories Network) scintillation counters.Each HELYCON station includes a GPS antenna, digitization and control electronics and the data acquisition system controlled by a PC.A single station is able to detect atmospheric showers initiated by cosmic particles of energy more than 10141015 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.GPSScintillator-PMTDAQ~20 m 1 m2 Station Server

Scintillator 2Scintillator 3GPS timestampStation ServerScintillator 4Scintillator 11 m2 active area scintillation counter.The ReadOut system is based on a HPTDC chip, designed at CERN,with 5 analogue inputs.The input signals are compared to six adjustable thresholds and the corresponding times of the PMT waveform-threshold crossings are digitized with an accuracy of 100ps.The synchronization between the HELYCON stations relies on the GPS time-signal which is incorporated in the data. The EAS Charged Particle Detector - DAQ

CORSIKA(Extensive Air ShowerSimulation)GEANT4(Scintillation, WLS & PMT response)Simulation Tools to describe the detector responseDAQSIM(DAQ Simulation)HOUANA(Analysis & ShowerReconstruction)The CORSIKA air shower simulation software is used to produce air showers, initiated by cosmic ray particles entering isotropically the upper atmosphere.Detector response, trigger formation, digitization and the Data Acquisition System is simulated by the specific HELYCON MC package.The events produced by the simulation are stored using the same format as the experimental data and they are analyzed in exactly the same way as real events.

Calibration and Test Results21 pes mean

Shower reconstruction Timing Corrections2 minimizationPlane wave Hypothesis

Time correctionsArrival Time Delay [ns]Deposited Charge [MIP]curvaturethickness

Observations of Extensive Air Showers - ResolutionThe performance of HELYCON in detecting and reconstructing showers has been studied by operating a system of eight HELYCON detectors in the laboratory. group A AMC=4.50.5o , group B BMC=5.20.6o, all six detectors 6MC=3.50.3o.

These resolutions can be evaluated solely from the real data, by comparing the results obtained by the two detector groups (A and B) on an event by event basis. The distribution of the difference (=-) of these two estimations of the zenith angle has a spread of DATA =7.20.2. This spread is consistent with the above MC predictions of the detector resolution:MC Estimated resolution= 7.20.2

Trigger Detectors >1.5 mip Detectors of groups A.and.B > 0.5 mipszenith angle [degrees]zenith angle [degrees]Trigger Detectors > 1.5 mipDetectors of groups A.and.B > 1.5 mips=9.40.2Observations of Extensive Air Showers

- Three Floating Stations operating independently above KM3NeT- Distance between stations 150m- 16m2 Scintillator Each StationSeaTop Detector Station Setup

Single Station Detection EfficiencyEfficiencyEventsA hit is considered when there is more than 4 mips deposited charge on a counter

Muon Propagation trackkm3Geant Simulation(propagation & Energy Loss)Accepted if muon with E>2TeV goes through km3Zenith angle < 13 degDetector response simulation and Muon Track Reconstruction

Monte Carlo Studies- Outlook 1014 - 51015 eVE~ 1014 - 51015 eV: 2500 showers/m2/yearSingle station detection: 360m2 geometrical area (effective area depends strongly on selection cuts)E> 1016 eV: 1 shower/m2/yearTO BE STUDIED35% of the detected showers include a muon which arrives at the Neutrino Telescope (depth 4000m) with an energy >300GeVGeneral Remark: 3 stations operating for 10 days can identify an angular offset of the KM3NeT with an accuracy of 0.05oSpecifically..

Investigation for a systematic angular offset of the KM3NeTWe use EAS that contain at least one energetic muon reconstructed by the KM3NeT and compare the estimated zenith angles of the shower axis and the muon track on an event by event basis.

The difference between these two angles should follow a normal distribution with mean zero. A possible statistically significant deviation from zero indicates that the estimations of the KM3NeT suffer from a systematic angular offset.The spread of this distribution expresses the calibration resolution per shower event.

Investigation for a systematic angular offset of the KM3NeTCalibration resolution per single shower event (degrees)na : minimum number of active detectors per shower eventEffective area of a floating detector stationThe calibration resolution per single shower decreases when events with more active detectors are selected because the reconstruction accuracy of the showers direction improves. However, the requirement of more active detectors per event results to a reduction of the effective area of the floating detector array.

minimum number of active detectors per shower event.Investigation for a systematic angular offset of the KM3NeTThe calibration resolution, c(na), in identifying a possible angular offset in the neutrino telescope estimations using the three floating detector arrays, is:For 3 EAS detector stations and 10 days of operation the calibration resolution has a minimum for na 5 .

The proposed calibration system will be able to measure a possible zenith angle offset with an accuracy of ~0.05o.

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

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

ConclusionsThe 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 degThe determination of the absolute position of the KM3NeT with an accuracy ~ 0.6 mEfficiency vs Energy and Zenith angle

SPASE air shower arrays calibration of AMANDA angular resolution and pointing ! resolution Amanda-B10 ~ 3.5spase-amanda

The Underwater Neutrino Telescope Working Example125mIceCube Geometry9600 OMs looking up & down in a hexagonal grid.80 Strings, 60 storeys each. 17m between storeysMultiPMT Optical Module20 x 3 PMTs (Photonis XP53X2) in each 17 Optical Module

I will report on the Use of floating surface detector stations for the calibration of a deep-sea neutrino telescope

The concept to use Extensive air shower detector arrays in cooperation with a neutrino telescope is actually taken from the SPASE-AMANDA project at the Antarctic sea. Some of the reconstructed showers by the EAS detector will also trigger the neutrino telescope array and a direct comparison can be made.The general idea of such a calibration module is that a significant percentage of the reconstructed atmospheric showers contain very energetic muons with energy grater than 2 TeV that can penetrate to the detector depth and can be reconstructed by the neutrino telescope.By comparing the reconstructed muon track with the reconstructed shower direction one can estimate in principle:The possible angular offset of the telescopeThe efficiency of the telesopeThe angular resolution and The absolute position of the telescope.In addition such arrays as I have already said can study Cosmic ray physics for example given thatthey will operate continuously for long periods of time. For that to be possible they should be installed on the nearest shore.Unfortunately this can not be done for a deep sea n-Telescope due to the required great incident zenith angles of the showers.Although the primary cosmic ray flux is isotropic, due to the atmosphere the zenith angle distribution is modulated according to this law with a of about 10, which means that showers which are not vertical enough are very rare. Moreover the produced by the EAS muon must have energy more than 1PeV to cross 20km water.So an array at the shore which must utilize almost vertical air showers is practically inappropriate for calibration purposesSo the concept of our proposal is the use of The HELYCON detector module consists of 160 scintillating tiles covering an area of about 1 m2. The light produced by the scintillator is guided to a single PMT with 96 Wavelength shifting fibers.The ReadOut system

Detailed Calibration of the scintillator counters have been performed in our laboratory. Using a small muon hodoscope (composed by to small scintillators A and B with lead shielding between), in order to indentify relativistic muons, we have estimated the local arrival time resolution and charge deposition of the response of the counters to a MIP. This local time resolution is 2ns as can been seen from this plot.It was found that the typical response of a HELYCON detector to a MIP corresponds to 21 photoelectrons with a variation of less than 10%, depending on the position of the muon hit.The charge deposited is in agreement with detailed MC predictions.The detector signals produced by extensive air showers are much larger than the pulses corresponding to a single MIP. By studying the distribution of the arrival time difference of these signals, the global time resolution and the slewing (systematic time offset) were also determined as a function of the charge of the PMT signal.

For the reconstruction we use the plane wave hypothesis and chi-square minimization, taking into account the curvature and thickness of the showers.The plane wave hypothesis is accurate enough for the shower reconstruction from a single station. We have parameterized the delay and the delay spread due to the curvature and thickness with respect to the collected charge.As you can see as the deposited charge is increased, the delay spread reaches a constant value which is actually the spread due to slewing.If we apply all these corrections and take into account the corresponding errors we cheked the procedure by calculating the time residuals of the detector hits.As you can see they are distributed according to a normal distibution with mean zero and sigma unity.The performance of HELYCON in detecting and reconstructing showers has been studied by operating a system of eight HELYCON detectors in the laboratory. In the setup shown in this figure the counters marked with a T provide the trigger, while we digitize the other six counters, splitted in 2 groups A and B.The analysis was focused on events when all six detectors were active. The shower axis direction was reconstructed by using: a) all six detectors, b) only the group of detectors Ac) only the group of detectors BAccording to the MC prediction the resolution in reconstructing the shower zenith direction for each group and all 6 detectors areWe have also estimated the zenith angle distributions of the showers reconstructed from each group, for different selection criteria, and we have found to be in acordance with published results.The setup of the Seatop detector used in this study is the following

In the left plot you can see the distribution of the active counters per shower and next The efficiency of the reconstruction with respect to the distance from the shower core.Each station can reconstruct showers which can be up to 60 meters far away from the center of the station.Only a portion of the reconstructed showers are usefull.Specifically we accept showers wich contain a muon with energy grater than 2 TeV with a direction towards the km3 detector.The most efficient position of the platform is found to be just above the v-telescope restricting us to showers with zenith angle less than 13 degrees. In the detailed MC studies we have simulated EAS with energies 10^14-5x10^15 eV. According to the cosmic ray flux spectrum the expected rate is 2500 showers/m2/year.One single station has a geometrical area 360m2, while the effective area depends strongly on the selection cuts. The MC studies show that 35% of the detected showers include a muon which arrives at the Neutrino Telescope (depth 4000m) with an energy >300GeV.Using the above mentioned station setup 3 stations operating for 10 days can identify an angular offset of the KM3NeT with an accuracy of 0.05 degrees.Specifically

One step further in the reconstruction analysis includes the deterimnation of the shower impact point.The impact point can be estimated by measuring the particle density distribution wit respect to the perpendicular core distance. This distribution can be parametrised according to the AGASA formulaWhere the parameters depend on the zenith angle the primary mass and the energy of the shower.However the mean lateral distribution for all energies and zenith angles can be parameterized with respect to the perpendicular distance from the shower coreAs you can see in these plots the mean particle density registered by an active counter as well as the rms value can be fitted very well. We have also estimated the calibration resolution in determining the absolute position of the neutrino detector. This is achieved by comparing the reconstructed impact point of the EAS and the point of intersection of the reconstructed muon track with the sea level surface.In these plots are shown In these results for the absolute positioning the effect of the GPS error has not been included. The conclusion is that the operation of 3 such stations for 10 days will provide:The determination of a possible offset with an accuracy ~ 0.05 degThe determination of the absolute position of the -detector with an accuracy ~ 0.6 m, while the resolution can be estimated through the inter-calibration technique.The concept is actually taken from the SPASE-AMANDA project at the Antarctic sea. The AMANDA detector is an array of Photomultiplier tubes that detect the Cherenkov light emmited by energetic muons that passing by. These muons may come from a neutrino interaction or more often these are atmospheric muons that penetrate to the detector depth.The Spase scintillation array consists of 120 scintillator counters positioned at the surface. They detect cosmic air showers in order to study the shower properties like energy, primary mass, age etc) but it also serves as a calibration module for the AMANDA detector.The concept is that some of the reconstructed showers will also trigger the AMANDA array and a direct comparison can be made. This way SPASE measured the AMANDA B10 reconstruction accuracy and also indicated a zenith angle offset of the neutrino detector of about 1.5 degrees.For the next generation of neutrino telescopes in the Antartic sea the ICECube collaboration designs the Icetop detector Being a part of IceCube, the main goals of IceTop sum up to be the following: Using the InIce-part of IceCube to scan the potential second-knee-regime in the Cosmic Ray Energy Spectrum for different primaries. Calibrating IceCube using coincident muon bundles and comparing reconstruction results. Enhance the noise detection of IceCube by providing a veto on muons generated by air showers above the telescope.