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Acoustic Properties of the South Pole Ice for Astrophysical Neutrino Detection

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Acoustic Properties of the South Pole Ice for Astrophysical Neutrino Detection FACULTEIT WETENSCHAPPEN Acoustic Properties of the South Pole Ice for Astrophysical Neutrino Detection Yasser M. Abdou Department of Physics and Astronomy, Faculty of Sciences, Ghent University Academic year 2011-2012 FACULTEIT WETENSCHAPPEN Acoustic Properties of the South Pole Ice for Astrophysical Neutrino Detection Yasser M. Abdou Promotor: Prof. Dr. Dirk Ryckbosch Thesis submitted in fulfilment of the requirements for the degree of Doctor in Sciences: Physics (PhD) Department of Physics and Astronomy, Faculty of Sciences, Ghent University Academic year 2011-2012 In memory of my father Acknowledgements First and foremost I would like to express my deepest gratitude to my supervisor Prof. Dirk Ryckbosch for accepting me as a member of his group and giving me a great oppor- tunity to work with IceCube project, the biggest neutrino telescope ever built. It has been an honor to be a Ph.D. student working with him. Thank you, Dirk for all encouragement and support you have given during my study. Many special thanks for all members of SPATS group who offered a great co-operation, discussion and guidance to establish my work. I have learned much from all of them in many ways and on many levels. I would like to acknowledge Dr. Julien Bolmont for his co-operation and guidance to use his adapted version of CORSIKA to perform the simulation study which presented in this work. Also, I would like to thank Dr. Tanguy Pierog, Dr. Dieter Heck and Dr. Johannes Knapp, the developer of the original version of CORSIKA, for their co- operation and patience which make me familiar with CORSIKA and be able to use it as it was needed to perform the simulation work. I also want to warmly thank all the members of the Department of Physics and As- tronomy at Ghent University. I have spent a very pleasant time during my study with all of you. It was very interesting to meet cool, funny and interesting people. Special thanks to IceCube mates for their encouragement and helpful discussions during my study and those from other experiments with whom I did not work, but shared nice moments at Monday morning meetings and annual group meetings. I would like to acknowledge Dr. Michael Carson, I appreciate all his time, ideas and discussion during my study to make this work visible. Also, I would like to thank him for his valuable suggestions he gave to me while reading my thesis. Special thanks goes to my office mate Dr. Michael Tytgat for his patience, encourage- ment, understanding and reading Dutch letters, frequently. I would like to thank all of my Egyptian friends at Ghent university and other friends from different nationalities for their friendship and assistance. Special thanks to Dr. Khaled Mostafa who welcomed and guided me to establish my new life in the beginning. My heartfelt gratitude to my parents, sister and brothers for their endless encourage- ments, support and patience. Special warm thanks to my beloved wife (Shereen) and my sweet kids (Mohamed and Kenzie) for their unending love, support and understanding during all the years of my study. I would also like to thank the members of the exam committee for their guidance, reading and suggestions to improve this thesis. Bedankt allemaal, Yasser iii iv Acknowledgements Contents ListofFigures..................................... vii ListofTables ..................................... xi Introduction 1 1 Cosmic Rays and Astrophysical Neutrinos 3 1.1 Highenergycosmicrays ............................ 3 1.2 Accelerationmechanism ............................ 5 1.3 NeutrinoAstronomy .............................. 7 1.3.1 Neutrinoproduction .......................... 7 1.3.2 GZKCut-off............................... 8 1.3.3 Cosmogenicneutrinoflux ....................... 9 1.3.4 Possible astrophysical neutrino sources . 14 1.3.5 Current neutrino flux limits . 17 2 Ultra High Energy Neutrino Detection 21 2.1 DeepInelasticScattering............................ 21 2.2 Cascades..................................... 22 2.2.1 Electromagneticcascade . 23 2.2.2 Hadroniccascade ............................ 23 2.2.3 LPMeffect ............................... 23 2.3 Neutrinodetectionmethods . .. .. .. 24 2.3.1 Opticalneutrinodetectors . 26 2.3.2 Radioneutrinodetectors . 28 2.3.3 Acousticneutrinodetectors . 32 2.4 SPATSandtheretrievabletransmitter . 34 2.4.1 Geometry ................................ 34 2.4.2 Hardware ................................ 34 2.4.3 Retrievable transmitter (Pinger) . 37 2.4.4 RecentSPATSresults ......................... 41 3 Acoustic Neutrino Detection 45 3.1 Thermo-acousticmodel............................. 45 3.2 Acousticsignalproduction ........................... 50 3.2.1 Acousticsignalproperties . 51 3.3 Iceproperties .................................. 52 3.3.1 Soundspeed............................... 54 3.3.2 Refraction................................ 56 3.3.3 Ambientnoise.............................. 56 3.3.4 Acousticsignalpropagation . 57 v vi CONTENTS 4 Pinger data analysis 63 4.1 Geometry .................................... 63 4.1.1 DepthMeasurements . .. .. 64 4.2 Laboratorytests ................................ 65 4.3 Dataacquisition................................. 66 4.4 Systematiceffects................................ 66 4.5 Dataprocessing................................. 70 4.5.1 Clock-driftcorrection. 70 4.5.2 Averaging ................................ 72 4.6 DataQuality:expectedsignal . .. .. 72 4.7 Attenuationanalysis .............................. 73 4.7.1 Datasetselection............................ 73 4.7.2 Fitting.................................. 75 4.7.3 Attenuation frequency dependence . 76 4.7.4 Attenuationresults ........................... 78 4.8 Soundspeedmeasurements. 84 4.8.1 Frequency dependent results . 86 4.8.2 Icefabricresults ............................ 89 4.9 Conclusion.................................... 92 5 Simulating the Acoustic Signal from Neutrino Interactions 93 5.1 Propagation and interaction of UHE neutrinos . .. 93 5.2 ModifiedCORSIKAinwater/ice . 94 5.3 Neutrino induced cascades in ice . 97 5.3.1 ACORNEparameterisation . 98 5.3.2 Showerpropertiesinice . 100 5.3.3 Longitudinal shower distribution . 100 5.3.4 Radial shower distribution . 102 5.4 Acousticsignal .................................103 5.4.1 Generation ...............................103 5.4.2 Attenuation ...............................107 5.4.3 Distancedependence . 109 5.4.4 Angulardependence . .. .. .112 5.5 Large acoustic neutrino detector simulation . 113 5.5.1 EffectivevolumeandGZKfluxes . 116 5.6 Conclusion....................................118 6 Discussion and outlook 121 A Discrete Fourier Transform 125 A.1 Basicequations .................................125 A.2 ContinuousFourierTransform . 125 A.3 DiscreteFourierTransform. 126 CONTENTS vii A.4 PowerSpectralDensity.............................126 A.5 RelationbetweenPSDandSignalRMS. 127 B Attenuation fit 129 C Simulation results 133 C.1 Longitudinalprofile...............................133 C.2 Radialprofile ..................................134 Bibliography 137 viii CONTENTS List of Figures 1.1 Cosmic ray spectrum for all particles. 4 1.2 UpdatedHillas(1984)diagram. .. .. 6 1.3 Energy loss lengths for UHE protons propagating through the universe. 9 1.4 Development of the proton energy with the travelled distance. ...... 10 1.5 Observation ofcut-offoncosmic rayspectrum. .... 11 1.6 TheGZKneutrinoflux. ............................ 13 1.7 DifferentGZKfluxmodels............................ 14 1.8 Unified scheme of the probable mechanism powering AGNs and GRBs. .. 15 1.9 UnifiedmodelofAGN.............................. 16 1.10 ThefireballshockmodelforGRBs. 17 1.11 Observational neutrino limits from IceCube-40. .... 18 1.12 Observational neutrino limits from acoustic and radio experiments. .... 19 2.1 The total νN cross-sectionathighenergy. 22 2.2 Cherenkovlightpatterns.. 25 2.3 TheIceCubedetector. ............................. 27 2.4 Schematic of the ANITA concept for UHE neutrino detection. ..... 29 2.5 ANITA-II neutrino flux limits. 30 2.6 Geometry of lunar neutrino cascade event detection. ...... 31 2.7 SchematicoftheSPATSarray.. 35 2.8 TheSPATSgeometry. ............................. 36 2.9 SPATSstage................................... 38 2.10 The pinger setup: view of the pinger stage and pinger in hole. .... 40 2.11 Sound speed for both pressure and shear waves. ...... 42 2.12 The transient events recorded by SPATS. .... 44 3.1 Schematic drawing of neutrino-induced cascade. .... 47 3.2 Soundwavesinsolids. ............................. 48 3.3 The acoustic bipolar pulse in water and ice. 51 3.4 The phase diagram of water and crystal structure of ice-Ih. ........ 53 3.5 Glacier ice crystal structure at different depths. ..... 53 3.6 Density and temperature profiles of the South Pole ice cap. ..... 54 3.7 Pressure waves profile and their ray trajectories in South Pole icecap.. 55 3.8 Sound speed vs the propagation angle relative the c-axis . .... 56 3.9 AbsorptioninSouthPoleice. ......................... 58 3.10 Absorption and scattering in South Pole ice. .. 59 4.1 The SeaStar and RW payout depth measurements for pinger hole 16. ... 65 4.2 Acoustic signal studies in the laboratory. .. 67 ix x LIST OF FIGURES 4.3 An example of a Clockdrift corrected average waveform . ..... 68 4.4 TheIRIG-B100ppstimingsignal. 71 4.5 Clock drift correction and waveform averaging. .... 72 4.6 Waveforms recorded by the same channel from different pinger holes. 74 4.7 Power spectra for signal, noise and noise-subtracted signal. ....... 77 4.8 The distribution of the
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