1. XXIII International Conference on Neutrino Physics and Astrophysics 2008 Christchurch, New Zealand Contacts: christopher.naumann@cea.fr gilles.maurin@cea.fr Detector Design Studies for a Cubic Kilometre Deep Sea Neutrino Telescope – KM3NeT J. Carr 1, F. Cohen 2, D. Dornic 1, F. Jouvenot 3, G. Maurin 4 and C. Naumann 4 for the KM3NeT consortium 1 CPPM – Centre de Physique des Particules de Marseille, CNRS/IN2P3, France 2 IReS - Institut de Recherches Subatomiques, Strasbourg, France 3 previously University of Liverpool, Oliver Lodge Laboratory – United Kingdom 4 CEA Saclay – DSM/IRFU – Service de Physique des Particules, France The case for a km 3 neutrino telescope Many known astrophysical objects such as AGNs, GRBs and SNRs, are expected to also produce TeV – PeV neutrinos by means of hadronic acceleration. Dark matter, accumulated in gravitational wells, is also expected to create neutrino signatures. In both cases, a detector volume of the order of cubic kilometres will be necessary. To achieve this goal, the European KM3NeT consortium is currently in the preparatory phase for the construction of a cubic-kilometre neutrino telescope in the Mediterranean Sea. Similar to its South Pole counterpart IceCube, it will be able to survey a large part of the galactic plane and the extragalactic sky, while its location on the northern hemisphere will also allow it to directly view the galactic centre. fixed: 127 strings variable: string spacing 3 optical modules = 10’’ PMTs variable tilt (9525 in total) 25 storeys, variable spacing Example: Hexagonal Geometry (m) XX Expected Performance (for NESSY Result) Hexagonal Configuration with - 225 strings spaced by 100 m - 25 storeys each, PMTs tilted 45° Hexagonal Configuration with - 225 strings spaced by 100 m - 25 storeys each, PMTs tilted 45° Towards a cubic kilometre detector in water scale up – too expensive – too complicated – not easily scalable (readout bandwidth, power,...) new design dilute absorption in water limits possible sensor spacing  sensitivity loss – effective area 2 - 3 x IceCube – muon angular resolution: 0.2° at 10 TeV – expected sensitivity after 1 year of data taking: 2.4 x 10 -12 TeV -1 cm -2 s -1 for generic E -2 sources – event rates for known TeV gamma sources (5 years):  test performance for various sets of geometry parameters Expected  fluxes require a detector volume of at least 1 km 3 … But: current sub-km 3 designs cannot just be scaled up !  Perform Monte-Carlo design study to establish optimised geometry New design optimised for: – sensitivity / cost – fast and easy installation – lifetime and stability Design Study with the “NESSY” tools – simulation and reconstruction/analysis chain – detailed semi-analytic simulation of light generation and propagation – originally developed in Mathematica (1) framework Fast and flexible approach to test a range of – physics parameters (absorption, scattering) – detector geometries – DAQ systems (thresholds, timing, etc) Fast and flexible approach to test a range of – physics parameters (absorption, scattering) – detector geometries – DAQ systems (thresholds, timing, etc) Distance between lines reconstruction detector simulation physics simulation water parameters ( abs, scattering ) background ( 40 K, biolum.) detector geometry front-end hardware photomultiplier tubes PMT configuration in the storey (number, distance, tilt)  effective area and angular resolution optimal string distance = 100 m (balance between total volume and density) optimum PMT configuration (for constant number of OMs): PMTs tilted by 45° (“standard”) N strings =const. (1) Wolfram Mathematica™ (www.wolfram.com) exemplary results for hexagonal test geometry 1 distance of PMT from string axis (standard=0.5 m) (1)