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

• 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

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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

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

• “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 bioluminescence40 K

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 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 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

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

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)

trigger

trigger level reco levelL1

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