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

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

high energy neutrino observation: motivation ν and γ 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

 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

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

KM3NeT: an artistic view

design aspects Multi-PMT Optical module 31 x 3” PMTs inside a 17” glass sphere Optical module 1Digital Optical Module=Dom 40Dom’s 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

“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 trigger

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

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

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

First trigger level reconstructed events L1 efficiency

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

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 Δt < 50 ns N_coincidences same floor / N_ OMs with L1-hit signal events: 30% noise: 0.8%

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

trigger: atmospheric muons 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 L2 Nevents reconstructed fulfilling L2 N events muon zenith angle L2 (3 local coincidences)

trigger trigger levelreco level L1 L2 L1 L2 ANIS no noise ANIS with noise

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