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Trigger issues for KM3NeT the large scale underwater neutrino telescope

Trigger issues for KM3NeT the large scale underwater neutrino telescope. E. Tzamariudaki NCSR Demokritos. the project objectives design aspects from the KM3NeT TDR trigger issues outlook. the project.

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Trigger issues for KM3NeT the large scale underwater neutrino telescope

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  1. Trigger issues for KM3NeTthe large scale underwater neutrino telescope E. Tzamariudaki NCSR Demokritos • the project • objectives • design aspects from the KM3NeT TDR • trigger issues • outlook

  2. the project • 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 ANTARES, NEMOandNESTORjoined efforts to prepare a km3-size neutrino telescope in the Mediterranean sea KM3NeT

  3. high energy neutrino observation: motivation ν andγproduced 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

  4. KM3NeT objectives • investigate neutrino “point sources” in the TeV energy regime • galactic Supernova Remnants, Microquasars • extragalactic Active Galactic Nuclei, Gamma Ray Bursts • High-energy diffuse neutrino flux • Field of view includes the Galactic center and complements IceCube • Optical properties of deep sea water: excellent angular resolution Neutrino cross section is extremely low very large active volume needed Instrumented volume of several km3 exceed IceCube sensitivity

  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

  6. KM3NeT: an artistic view

  7. design aspects Multi-PMT Optical module 1 Digital Optical Module = Dom 40 Dom’s on 1 tower = Dom tower storey Optical module 31 x 3” PMTs inside a 17” glass sphere • Multi-PMT OM advantages • separation of single-photon and multi-photon hits • information on the arrival direction better track reconstruction

  8. trigger • “All-data-to-shore” concept • Trigger • Multi-PMT optical module: • L1: coincidence of ≥ 2 hits in one optical module (Δt ≤ 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 (Δt ≤ 50 ns) • Local coincidences of L1 hits on OMs on neighbouring floors

  9. ANTARES trigger studies noise: background from decays and from bioluminescence • anis neutrino generator: no noise and noise-only • anis neutrino generator with noise • atmospheric muon background (MUPAGE) with noise

  10. trigger: number of hits on an OM neutrino events (no noise) noise only number of hits number of hits number of hits on an OM hits within 40 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) hits within 10 ns

  11. First trigger level 5 OMs with hits 5 OMs with L1 hits trigger level zenith angle 1 OM hit 1 OM with L1 hit 5 OMs hit 5 OMs with L1 hit

  12. First trigger level L1 efficiency reconstructed events

  13. second trigger level • 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 L1 PMT vicinity cut trigger level well reconstructed events 98% of well reconstructed events fulfill this requirement

  14. second level trigger • apply a requirement on local coincidences of L1 hits on both OMs of the bar Δt < 50 ns trigger level L1 1, 2, 3 such local coincidences require 1, 2, 3 such local coincidences signal events: 30% N_coincidences same floor / N_OMs with L1-hit noise: 0.8%

  15. trigger • vicinity of the PMTs hit on an OM and L2 requirements: • 2 local coincidences of L1 hits on both OMs of the bar trigger level 2, 3 local coincidences on bar OMs reco level

  16. trigger: atmospheric muons • vicinity of the PMTs hit on an OM and L2 requirements: • 2 local coincidences of L1 hits on both OMs of the bar N events muon zenith angle Nevents @ L2 Nevents @ L2 (3 local coincidences) Nevents @ L1 Nevents reconstructed Nevents reconstructed fulfilling L2

  17. trigger L1 L1 trigger level reco level L2 L2 ANIS with noise ANIS no noise

  18. Conclusions and outlook KM3NET Collaboration • 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 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…

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