INO/2006/01 Project Report Volume I INDIA-BASED NEUTRINO OBSERVATORY INO Cover Design: B.K. Chavan, N.K. Mondal ——————————- The INO Collaboration1 Aligarh Muslim University, Aligarh: • M. Sajjad Athar, Rashid Hasan, S. K. Singh Banaras Hindu University, Varanasi: • B. K. Singh, C. P. Singh, V. Singh Bhabha Atomic Research Centre (BARC), Mumbai: • V. Arumugam, Anita Behere, M. S. Bhatia, V. B. Chandratre, R. K. Choudhury, V. M. Datar, M. P. Diwakar, M. G. Ghodgaonkar, A. K. Mohanty, A. W. Matkar, P. K. Mukhopadhyay, S. C. Ojha2, L. M. Pant, K. Srinivas Calcutta University (CU), Kolkata: • Amitava Raychaudhuri Delhi University (DU), Delhi: • Brajesh Choudhary, Debajyoti Choudhury, Sukanta Dutta, Ashok Goyal, Kirti Ranjan Harish Chandra Research Institute (HRI), Allahabad: • Sanjib K. Agarwalla, Sandhya Choubey, Anindya Datta, Raj Gandhi, Pomita Ghoshal, Srubabati Goswami, Poonam Mehta, Sukanta Panda, S. Rakshit, Amitava Raychaud- huri University of Hawaii (UHW), Hawaii: • Sandip Pakvasa Himachal Pradesh University (HPU), Shimla: • S. D. Sharma Indian Institute of Technology, Bombay (IITB), Mumbai: • Basanta Nandi, S. Uma Sankar, Raghav Varma Indira Gandhi Center for Atomic Research, Kalpakkam: • J. Jayapandian, C. S. Sundar The Institute of Mathematical Sciences (IMSc), Chennai: • D. Indumathi, H. S. Mani, M. V. N. Murthy, G. Rajasekaran, Nita Sinha, D. V. Ra- makrishna 3 Institute of Physics (IOP), Bhubaneswar: • Pankaj Agrawal, D. P. Mahapatra, S. C. Phatak North Bengal University (NBU), Siliguri: • A. Bhadra, B. Ghosh, A. Mukherjee, S. K. Sarkar 1This is an open collaboration and experimentalists are especially encouraged to join. 2since retired 3Replacing Abdul Salam who was a member until March 5, 2005 Panjab University (PU), Chandigarh: • Vipin Bhatnagar, M. M. Gupta, J. B. Singh Physical Research Laboratory (PRL), Ahmedabad: • A. S. Joshipura, Subhendra Mohanty, S. D. Rindani Saha Institute of Nuclear Physics (SINP), Kolkata: • Sudeb Bhattacharya, Suvendu Bose, Sukalyan Chattopadhyay, Ambar Ghosal, Asimananda Goswami, Kamales Kar, Debasish Majumdar, Palash B. Pal, Satyajit Saha, Abhijit Samanta, Abhijit Sanyal, Sandip Sarkar, Swapan Sen, Manoj Sharan Sikkim Manipal Institute of Technology, Sikkim: • G. C. Mishra Tata Institute of Fundamental Research (TIFR), Mumbai: • B. S. Acharya, Sudeshna Banerjee, Sarika Bhide, Amol Dighe, S. R. Dugad, P. Ghosh, K. S. Gothe, S. K. Gupta, S. D. Kalmani, N. Krishnan, Naba K. Mondal, P. Nagaraj, B. K. Nagesh, Biswajit Paul, Shobha K. Rao, A. K. Ray, L. V. Reddy, B. Satyanarayana, S. Upadhya, Piyush Verma Variable Energy Cyclotron Centre (VECC), Kolkata: • R. K. Bhandari, Subhasish Chattopadhyay, Premomay Ghosh, B. Mohanty, G. S. N. Murthy, Tapan Nayak, S. K. Pal, P. R. Sarma, R. N. Singaraju, Y. P. Viyogi Scientific Steering Committee C. V. K. Baba, Nuclear Science Centre, New Delhi Ramanath Cowsik, Indian Institute of Astrophysics, Bangalore H. S. Mani, The Institute of Mathematical Sciences, Chennai V. S. Narasimham, Tata Institute of Fundamental Research, Mumbai G. Rajasekaran, The Institute of Mathematical Sciences, Chennai Amit Roy, Nuclear Science Centre, New Delhi Probir Roy, Tata Institute of Fundamental Research, Mumbai Bikash Sinha, Saha Institute of Nuclear Physics, Variable Energy Cyclotron Centre, Kolkata INO Spokesperson Naba K Mondal, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India E-mail: [email protected] E-mail: [email protected] URL: http://www.imsc.res.in/ ino ∼ iv v Each one of us adds a little to our understanding of nature and from all the facts assembled arises a certain grandeur. Aristotle PREFACE Very important developments have occurred recently in neutrino physics and neutrino astronomy. Oscillations of neutrinos and the inferred discovery that neutrinos have mass are likely to have far-reaching consequences. This discovery has come from the study of neutrinos from the Sun and those produced by cosmic rays. The pioneering solar neutrino experiments of Davis and collaborators in the USA, the gigantic Super-Kamiokande detector and the KamLAND detector in Japan, the heavy-water detector at the Sudbury Neutrino Observatory in Canada, and a few other laboratories, together, have contributed in a very fundamental way to our knowledge of neutrino properties and interactions. In particular, the Canadian experiment has given direct experimental proof of the 80 year-old hypothesis that the Sun and the stars are powered by thermonuclear fusion reactions. Impelled by these discoveries and their implications for the future of particle physics, plans have been made—world-wide—for new neutrino detectors, neutrino factories and long base-line neutrino experiments. Indian scientists were pioneers in neutrino experiments. In fact neutrinos produced by cosmic ray interactions in the Earth’s atmosphere were first detected in the deep mines of the Kolar Gold Fields (KGF) in India in 1965. It is planned to revive underground neutrino experiments in India. A multi-institutional Neutrino Collaboration has been formed with the objective of creating an India-based Neu- trino Observatory (INO). This Report is based on the feasibility study conducted by the collaboration. The report discusses specific physics goals both for the near term and the future. More information may be found on the INO web-site: http://www.imsc.res.in/ ino. ∼ This is an open collaboration and it is hoped that many more physicists from within and outside the country will join in this effort. The success of this project crucially depends upon international participation and support. Note added: This report is an updated and revised version of the Interim Report Vol I, submitted to the Department of Atomic Energy (DAE), Department of Science and Technol- ogy (DST) and University Grants Commission (UGC), of the Government of India, on May 1, 2005. Major additions have been made to the Physics, Detector and Simulation chapters with some minor changes elsewhere. vi Contents 1 Project Summary 1 1.1 OrganisationoftheReport. 3 1.2 SummaryofcurrentstatusofINO. 5 1.3 AvisionforINO ................................. 5 2 Introduction 7 2.1 Current Status of neutrino physics experiments . ........ 8 2.2 Openquestionsandfuturegoals. 10 3 Neutrino Physics with Magnetised Iron Calorimeter 15 3.1 Three flavour neutrino oscillation . ..... 16 3.2 Parameter values gleaned from experiments . ....... 16 3.3 AtmosphericNeutrinos .............................. 19 3.3.1 Precision measurement of δ and θ ................. 21 | 32| 23 3.3.2 Matter effects in µ− and µ+ events ................... 24 3.3.3 Determination of mass hierarchy . 27 3.3.4 Deviation from maximality of θ23: octant determination . 34 3.3.5 Discrimination between ν ν and ν ν ............. 40 µ → τ µ → s 3.3.6 ProbingCPTViolation. 40 3.3.7 Constraining long-range leptonic forces . ...... 43 3.4 NeutrinoFactories ................................ 46 3.4.1 Determination of θ13 ........................... 48 3.4.2 Sign of δ32 ................................. 50 3.4.3 Probing CP violation in the leptonic sector . ..... 50 3.5 Large matter effects in ν ν oscillations................... 52 µ → τ 4 Other Physics issues with Magnetised Iron Calorimeter 59 4.1 Probing cosmic rays through muons underground . ...... 59 4.1.1 The cascade event rate for muons with energies 1–1000 TeV ..... 61 4.1.2 MuonFluxes ............................... 64 4.1.3 ResultsandDiscussion .......................... 65 4.2 Kolarevents.................................... 66 5 The Magnetised Iron Calorimeter 69 5.1 Choiceofthedetector ............................. 69 5.2 TheICALDetector................................ 70 5.2.1 Basicparameters ............................. 70 5.2.2 RPCs as active detector elements . 71 5.2.3 Detector arrangement and readout schemes . 73 5.2.4 ReadoutElectronics ........................... 74 vii viii CONTENTS 5.2.5 VoltageComparatorASIC . 75 5.2.6 GasSystem ................................ 75 5.2.7 Structural stability of ICAL detector . 76 5.3 CurrentstatusofdetectorR&D . 76 5.3.1 Gasmixingunits ............................. 76 5.3.2 RPC operation and characterisation . 79 5.3.3 LongtermstabilitytestsofINORPCs . 84 5.3.4 Tracking of cosmic ray muons using small size RPCs . 84 5.3.5 ICALPrototype.............................. 88 5.4 TheMagnet.................................... 89 5.4.1 Designcriteria............................... 90 5.4.2 A toroidal design for the ICAL magnet . 91 5.4.3 A small magnet for detector prototype tests . 93 5.4.4 FinalDesign................................ 98 6 ICAL Simulations 101 6.1 Thedetectorgeometry ............................. 101 6.1.1 Digitisationoftracks . 102 6.2 Theneutrinosource................................ 103 6.2.1 Theatmosphericneutrinoflux . 103 6.2.2 Eventsgeneration............................. 104 6.2.3 Muonenergydistribution . 104 6.2.4 Muonzenithangledistribution . 104 6.3 Eventtrackingandreconstruction . 107 6.3.1 Reconstruction of test events . 107 6.3.2 Muonenergyreconstruction . 107 6.3.3 Muondirectionreconstruction . 110 6.3.4 Muonchargeidentification . 111 6.3.5 Hadronenergycalibration . 112 6.4 AtmosphericneutrinoanalysiswithGEANT . 113 6.4.1 DataAnalysis............................... 114 6.4.2 L and E resolutions ........................... 114 6.4.3 The oscillation parameters . 116 6.4.4 PrecisionPlots .............................. 117 6.5 Cosmicraymuons ................................ 118 6.5.1 Thesurfacemuonflux .......................... 119 6.5.2 Cosmicraysunderground . 120 6.5.3