The observation of the universe is traditionally done through photons. These neutral particles are not deviated by intergalactic magnetic fields and thus allow the study of precise point sources. But the more their energy increases (gamma domain), the more their penetration power diminishes: only the outer layers of the objects are visible and over shorter and shorter distances. The distant high energy sky ,that of the cataclysmic phenomena of the childhood of the Universe, is concealed from the astronomer.
But a new messenger, the neutrino, could soon snatch these mysteries. Neutral and light, the neutrino has the same qualities as the photons. Its advantage lies in its penetrating character, linked to its low effective interaction cross-section of with matter. This gives it both the possibility of excaping from the densest zones of the Universe and of traversing cosmological distances without suffering any alteration. The neutrino is also therefore very difficult to capture.
Estimates have shown that it is necessary to construct a telescope of about 1 km3 to detect a few, and to bury it deep in the sea to protect itself from the sheaves of atmospheric particles. This was confirmed by the detection in 2013 by the ICECUBE experiment of the first neutrinos of very high energy of astrophysical origin, thus giving at the same time birth to the astronomy neutrino.
The European collaboration ANTARES chose to place a more modest version at 2500 m at the bottom of the sea, to prove the feasibility of such an experiment. This telescope comprises 12 detection lines harnessed with photomultipliers intended to identify the path of light left by the daugther particles of the neutrinos after their interaction in the vicinity. The telescope has been completed since mid 2008, but the data acquisition started as soon as the first detection line was immersed in 2007. The APC laboratory participates in the operation of the telescope, data acquisition, analysis and interpretation.
At the same time, the group is participating in the development of the future 1 km3 telescope in the KM3NeT collaboration. The group is involved in the development of the Oscillation Research with Cosmics in the Abyss, an underground Cherenkov neutrino detector, expected to be part of the distributed KM3NeT infrastructure. It will be devoted to the study of the fundamental properties of neutrinos, exploiting the abundant flux of neutrinos produced in the interactions of the cosmic rays with the atmosphere.
The atmospheric flux of neutrinos has traditionally been considered as background noise for the detection of an astrophysical neutrino signal. In recent years, however, it has been realized that in the GeV band this flow holds the key to solving a fundamental question of particle physics: that of the neutrino mass hierarchy, The normal state v3 of the mass is heavier (normal hierarchy) or lighter (inverted hierarchy) than the states ν2 and ν1 The influence of the mass hierarchy on the oscillations of neutrinos in matter leaves its imprint on the flow Of atmospheric neutrinos via the characteristic appearance of the appearance / disappearance of the various types of neutrinos as a function of the energy and the path traversed through the earth.
To do this, ORCA plans to instrument a multi-megaton scale array of optical modules based on KM3NeT technology and optimized for the study of interactions between atmospheric neutrinos in the sea. The optical modules will be placed in a dense configuration, with an energy threshold of the order of the GeV, three orders of magnitude lower than the standard energy scale tested by ARCA for neutrino astronomy. To be deployed at the French site of KM3NeT, ORCA's multi-PMT optical modules will benefit from the excellent optical properties of deep sea water to achieve the angular and energy resolutions needed to illuminate the mass hierarchy of neutrinos.
Phase 1 of KM3NeT provides for the deployment and operation of a prototype array for ORCA, comprising 7 detection lines with 20 m line spacing in the next two years. If the funds allow, the complete ORCA detector, consisting of a KM3NeT building block (115 detection lines), could be operational by the end of the decade, offering new possibilities for oscillation studies Neutrinos in the Mediterranean, complementary to reactor and beam experiments.
Permanent Staff at APC
- BARET Bruny
- CREUSOT Alexandre
- DONZAUD Corinne
- KOUCHNER Antoine
- LACHAUD Cyril
- LOUCATOS Sotiris
- VAN ELEWYCK Véronique (head of the group)
Egineers & technicians:
- COELHO Joao (post-doc projet ONSET IdEx Sorbonne Paris Cite)
- COLEIRO Alexis (now also at lFIC Valencia, Spain)
- AVGITAS Théodore (2014-2017): Characterization and calibration of the ANTARES and KM3NeT optical modules and their impact on the detection efficiency of the telescopes.
- BOURRET Simon (2015-2018): Tomography of the Earth's core with ORCA
- GREGOIRE Timothée (2015-2018): Search for neutrinos coming from the interaction of the cosmic radiation during its propagation in the galaxy in the data of ANTARES
- AUBLIN Julien (LPNHE - Université Paris 6)
- VALLAGE Bertrand (IRFU-CEA)
- GAY Pascal (LPC Clermont-Ferrand/Université Blaise Pascal)
- GALATA Salvatore (post-doc 2014-2016): Reconstruction algorithms and Monte Carlo simulations for KM3NeT
- GARCIA RUIZ Rodrigo (PhD 2013-2016):
- BOUHOU Boutayeb: Joint search for Coincident High Energy neutrino and Gravitational Waves: https://tel.archives-ouvertes.fr/tel-00819985v1
- PICQ Claire
- MOSCOSO Luciano
- Characterization of photodetectors
- Single photoelectron efficiency PMT maps
- Afterpuls studies.
- 8m^3 water tank with hodoscope for OM and DOM characterisation thanks to cosmic muons Cherenkov light.
- Detector studies:
- Detector efficiency evolution.
- Data analysis and calibration of fist KM3NeT lines
- Physics studies for KM3NeT
- ORCA sensitivity to neutrino mass hierarchy
- Earth core tomography (projet ONSET en collaboration avec l'IPGP)
- Data analysis
- Joint High Energy neutrinos and Gravitational Waves searches (on-line and offline).
- Auto and Cross correlations studies and constrints on source populations
- Search for neutrinos from the galactic ridge
Responsabilities in ANTARES/KM3NeT
- A. Kouchner:
- Spokesman of the ANTARES collaboration
- ORCA prospective study coordinator
- B. Baret:
- coordinator with B. Vallage dof the ANTARES calibration working group
- coordinator of the Gamma Ray Bursts sub working group ofANTARES
- member of the KM3NeT Publication Committee
- V. Van elewyck:
- ANTARES Data Quality working group coordinator
- Chair of the ANTARES publication committee
- Publications of group members (no filter, from inspirehep)
- Publications ANTARES.
- Publications KM3NeT
- Publications High Energy Neutrinos and Gravitational Waves (GWHEN).
- Publications on Mass Hierarchy detecrmination with ORCA.