Slide 1

Trigger issues for KM3NeT the large scale underwater neutrino telescope the project objectives design aspects from the KM3NeT TDR trigger issues outlook E. Tzamariudaki NCSR Demokritos Slide 2 The KM3NeT Consortium aims at developing a large deep-sea infrastructure at the Mediterranean sea. A multi-cubic-kilometer Cherenkov telescope for the discovery of sources of high-energy (>100GeV) cosmic neutrinos. Long-term measurements in the area of oceanography, marine biological sciences and geophysics the project ANTARES, NEMO and NESTOR joined efforts to prepare a km3-size neutrino telescope in the Mediterranean sea KM3NeT Slide 3 high energy neutrino observation: motivation and produced in the interaction of high energy nucleons with matter or radiation cosmic ray acceleration yields neutrinos and gammas with similar abundance and energy spectra neutrinos: unique messengers Slide 4 investigate neutrino point sources in the TeV energy regime KM3NeT objectives galactic Supernova Remnants, Microquasars extragalactic Active Galactic Nuclei, Gamma Ray Bursts Field of view includes the Galactic center and complements IceCube Optical properties of deep sea water: excellent angular resolution High-energy diffuse neutrino flux Neutrino cross section is extremely low very large active volume needed Instrumented volume of several km3 exceed IceCube sensitivity Slide 5 high energy neutrino observation Upward-going neutrinos interact in rock or water charged particles (in particular muons) produce Cherenkov light in water at 43 with respect to the neutrino direction light is detected by array of photomultipliers muon direction is reconstructed using PMT positions and photon arrival times the Earth provides screening against all particles except neutrinos the atmosphere acts as target for production of secondary neutrinos Slide 6 KM3NeT: an artistic view Slide 7 design aspects Multi-PMT Optical module 31 x 3 PMTs inside a 17 glass sphere Optical module 1Digital Optical Module=Dom 40Doms on 1 tower=Dom tower storey Multi-PMT OM advantages separation of single-photon and multi-photon hits information on the arrival direction better track reconstruction Slide 8 All-data-to-shore concept Trigger Multi-PMT optical module: L1: coincidence of 2 hits in one optical module (t 10 ns) Consider coincidences of 2 neighbouring or next-to-neighbouring L1 hits Bar provides for easy level 2 filter Local coincidences of 2 L1 hits on one bar (t 50 ns) Local coincidences of L1 hits on OMs on neighbouring floors trigger Slide 9 trigger studies anis neutrino generator: no noise and noise-only anis neutrino generator with noise atmospheric muon background (MUPAGE) with noise noise: background from decays and from bioluminescence ANTARES Slide 10 trigger: number of hits on an OM neutrino events (no noise)noise only number of hits on an OM hits within 40 ns hits within 10 ns noise: 80% of OMs have 2 hits but only 2% are within 10ns signal: 42% of OMs have 2 hits; > 60% within 10ns (1-10TeV) number of hits Slide 11 First trigger level 5 OMs with hits 5 OMs with L1 hits trigger level 1 OM hit 1 OM with L1 hit 5 OMs hit 5 OMs with L1 hit zenith angle Slide 12 First trigger level reconstructed events L1 efficiency Slide 13 second trigger level trigger level L1PMT vicinity cut well reconstructed events apply a requirement on the vicinity of the PMTs hit on an OM: require 5 OMs with 2 L1 hits on (next-to-)neighbouring PMTs 98% of well reconstructed events fulfill this requirement Slide 14 second level trigger apply a requirement on local coincidences of L1 hits on both OMs of the bar require 1, 2, 3 such local coincidences trigger level L1 1, 2, 3 such local coincidences t < 50 ns N_coincidences same floor / N_ OMs with L1-hit signal events: 30% noise: 0.8% Slide 15 trigger trigger level L2 requirements: vicinity of the PMTs hit on an OM and 2 local coincidences of L1 hits on both OMs of the bar reco level 2, 3 local coincidences on bar OMs Slide 16 trigger: atmospheric muons Nevents @ L1 L2 requirements: Nevents reconstructed vicinity of the PMTs hit on an OM and 2 local coincidences of L1 hits on both OMs of the bar Nevents @ L2 Nevents reconstructed fulfilling L2 N events muon zenith angle Nevents @ L2 (3 local coincidences) Slide 17 trigger trigger levelreco level L1 L2 L1 L2 ANIS no noise ANIS with noise Slide 18 A design for an underwater neutrino telescope at the Mediterranean has been developed and the KM3NeT TDR has been published Optimization efforts for the final design definition are converging A prototype (PPM) is currently under construction Conclusions and outlook KM3NET trigger Multi-PMT optical module offers several possibilities - use local coincidences in space and time bar can be used for an efficient level 2 filter noise contribution can be suppressed significantly work on trigger optimization still ongoing Collaboration