Trigger issues for KM3NeT the large scale underwater neutrino telescope
description
Transcript of Trigger issues for KM3NeT the large scale underwater neutrino telescope
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Trigger issues for KM3NeTthe large scale underwater neutrino telescope
Trigger issues for KM3NeTthe large scale underwater neutrino telescope
• the project
• objectives
• design aspects from the KM3NeT TDR
• trigger issues
• outlook
E. Tzamariudaki
NCSR Demokritos
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• 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
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high energy neutrino observation: motivation
ν and γ produced in the interaction of high energy nucleons with matter or radiation
0 N X Y Y
cosmic ray acceleration yields neutrinos and gammas with similar abundance and energy spectra
neutrinos:
unique messengers
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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
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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
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KM3NeT: an artistic view
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design aspects
Multi-PMT Optical module
31 x 3” PMTs inside a 17” glass sphere
Optical module
1 Digital Optical Module = Dom40 Dom’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
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• “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
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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 bioluminescence40 K
ANTARES
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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 number of hits
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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
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First trigger level
reconstructed events
L1 efficiency
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second trigger level
trigger level L1 PMT 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
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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%
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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
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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 e
ven
ts
muon zenith angle
Nevents @ L2 (3 local coincidences)
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trigger
trigger level reco levelL1
L2
L1
L2
ANIS no noise ANIS with noise
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• 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