NEMO Experiment Research Articles

About the Negative Gravitational Mass

In a previous paper, we demonstrated that the linearized general relativity could explain dark energy (the experimental values of parameters ΩΛ, the cosmological constant, the recent acceleration of the expansion of our Universe) offering an amazing image of our universe at an incredible scale. This explanation of dark energy relies on the assumption of the existence of a negative gravitational mass (with always a positive inertial mass meaning that gravitation could be repulsive). This article demonstrates that this assumption is not only compliant with general relativity but even that the repulsive gravitational interaction is inscribed in the equations of the general relativity. The absence of negative gravitational mass should then be justified because nothing forbids its existence and until now repulsive gravitation has never been observed. This natural possibility of general relativity must be then avoided by adding an ad hoc paradigm. In a way, the principle of masses’ equivalence plays indirectly this role. We will show why this principle can be verified with a great accuracy but we also propose experiments that could violate this principle, allowing at the same time rejecting its status of theoretical principle. This frame of explanation (general relativity released from this ad hoc constraint) opened then the way of the negative gravitational mass with its natural corollary, the repulsive gravitational interaction, and of the following major predictions: the antimatter should have a negative gravitational mass, the neutrino should not be a Majorana particle, the principle of equivalence of masses should be violated for the antiprotonic helium, the apparent disappearance of antimatter could be explained. We recall some other consequences: an “initial” cosmic inflation would be unavoidable, dark energy (or cosmological constant) might not be constant in time (causing accelerating universe). Several experiments are testing some of these predictions: NEMO experiment tests if neutrino is a Majorana particle, and AEgIS, ALPHA and GBAR experiments at CERN test the behavior of the gravitational interaction on anti-matter and the sign of its gravitational mass. First results could be obtained in 2018. Experiments are proposed to test the violation of the principle of equivalence of the masses.

Acoustic Detection of Neutrinos: Review and Future Potential

The acoustic neutrino detection technique is a promising approach for future large-scale detectors with the aim of measuring the small expected flux of cosmogenic neutrinos at energies exceeding 100 PeV. The technique is based on the thermo-acoustic model, which implies that the energy deposition by a particle cascade—resulting from a neutrino interaction in a medium with suitable thermal and acoustic properties—leads to a local heating and a subsequent characteristic pressure pulse that propagates in the surrounding medium. The main advantage of using sound for the detection of neutrino interactions, as opposed to Cherenkov light, lies in the much longer attenuation length of the former type of radiation: several kilometres for sound compared to several ten metres for light in the respective frequency ranges of interest in sea water. As detection media for future detectors, water, ice, salt domes and permafrost have been discussed, but it is the first two which have been investigated most thoroughly by using existing arrays of acoustic receivers—mainly military arrays in various bodies of water—or by implementing dedicated acoustic arrays in Cherenkov neutrino telescopes. Such arrays have been installed in IceCube at the South Pole, in the Lake Baikal experiment in Siberia and in ANTARES and the former NEMO experiment in the Mediterranean Sea. The future KM3NeT neutrino telescope to be installed in the Mediterranean Sea will be equipped with acoustic sensors for position calibration that are suited to also serve acoustic detection purposes. Ongoing experiments in water and ice have established the feasibility of the acoustic neutrino detection technique and allowed for the investigation of prevailing background conditions. Methods to improve the signal detection efficiency and to reduce the rate of misidentified neutrinos have been devised and potential future large-scale detector designs are investigated using detailed simulations in combination with the wealth of collected experimental data. In this presentation, a brief review of acoustic particle detection, considering both theoretical and experimental aspects, will be given. The current status and plans for the future will be discussed.

Performance Analysis of a DWDM Optical Transmission System

Dense wavelength division multiplexing (DWDM) is an optical technology that allows transmitting across a fiber many wavelengths, which can be added and dropped by means of passive optical components. We present and discuss the performance of a complex DWDM network data transmission system that will find an application in the NEMO underwater neutrino telescope. The tests cover the qualification of a complete multipoint DWDM network consisting of transponders, fibers, passive optical filters, and an optical amplifier. The behavior of the network is evaluated in the final arrangement by means of bit error ratio (BER) and optical signal-to-noise ratio measurements at 800 Mb/s rate. In order to test the network, a board, developed for the NEMO experiment, has been used. A custom DWDM module, capable of data rates up to 1.4 Gb/s and specifically designed for real-time data acquisition systems, can be hosted by the board. A dedicated application runs on the board programmable logic controlling the module, monitoring the transceiver's functionalities and running the BER test.

The data acquisition and transport design for NEMO Phase 2

Many high energy physics experiments (Auger, IceCube, NEMO, Km3Net) currently taking data or planned in the near future consist of big and sparse detectors that acquire a huge amount of data. This kind of topology requires the ability to acquire physics information in different places of the detector and correlate them using the occurrence time, usually with a sub-ns precision. The architecture described here provides a real-time data transport layer, used to implement the data acquisition system for the NEMO experiment, and consists of a synchronous link with fixed and deterministic latency. The system clock, distributed at every level of the apparatus, has been derived by the signals provided by a GPS receiver during the operating configuration. The aim of this contribution is to give an overview of the NEMO electronic system: the underwater electronics sample signals from photomultipliers and acquires slow-control data from both oceanographic instruments and dedicated sensors, allowing to monitor the operational conditions of the apparatus. The whole data are sent to the laboratory through a fully bi-directional fiber optic link. On-shore the data are received by dedicated boards that distribute them to the first-level trigger and to the slow-control system. A description of the different stages of data acquisition and transport will be given.

PORFIDO: Oceanographic data for neutrino telescopes

PORFIDO (Physical Oceanography by RFID Outreach) is a system designed to be installed in the optical modules of the NEMO experiment and possibly, in future underwater neutrino telescopes to gather oceanographic data with a minimum of disturbance to the main project and a very limited budget. The system gathers oceanographic data (temperature, etc.) from passive RFID tags (WISPs) attached to the outside of the NEMO optical modules with an RF reader situated inside the glass sphere, without the need of connectors or penetrators, which are very expensive and offer low reliability. Ten PORFIDOs will be deployed with the NEMO Phase 2 tower in 2011.

Towards a km3 scale neutrino detector in the Mediterranean: NEMO and KM3NeT

Neutrinos are promising probes for high energy astrophysics. According to present estimates, km3 scale detectors are needed to detect high energy cosmic neutrinos. Deep water/ice Cherenkov technique was proposed to detect high energy neutrinos through the tracking of the secondary muons produced in neutrino interactions. The IceCube neutrino telescope is under construction at the South Pole. For a full sky observation, a second km3 telescope is required in the Northern hemisphere. In this paper progress and latest results from the NEMO experiment as well as the status of the KM3NeT European consortium activities toward a km3 telescope in the Mediterranean Sea are presented.

The NEMO-3 experiment and the SuperNEMO project

The NEMO experiment investigates the neutrinoless double beta decay. The NEMO-3 detector is collecting data in the Frejus Underground Laboratory. The goal of the SuperNEMO detector is to reach a sensitivity of the order of 10 26 year on the half-life of the β β 0 ν process. The chosen isotopes for the future detector are 82Se and 150Nd, because of the reduced background. The collaboration has started a 3-year R& D development on all components: tracking detector, calorimeter, source enrichment and purification and radiopurity measurements.

Data taking system for the NEMO experiment

A four-floors prototype of the NEMO towers has been successfully deployed off the Sicily coast in December 2006. The aim of this contribution is to give an overview of the NEMO electronic system and to explain the different stages of data acquisition and transport.The underwater electronics sample signals from photomultipliers and acquire slow-control data both from oceanographic instruments and dedicated sensors, allowing to monitor the operational conditions of the apparatus.The whole data are sent to the laboratory through a fully bi-directional fiber optic link. On-shore the data are received by dedicated boards that distribute them to first-level trigger and to the slow-control system.The NEMO data acquisition/transmission electronic system will be described, properties of acquired signals and of data flow will be discussed.

Status of the NEMO experiment

The activities towards the realisation of a km 3 Cherenkov underwater neutrino detector, carried out by the NEMO collaboration are described. The validation of the proposed technical solutions (NEMO Phase-1) and a detailed study of the candidate site have been undertaken (NEMO Phase-2).

Influence of neutrons and γ-rays in the Fréjus underground laboratory on the NEMO experiment

To be sensitive to an effective Majorana neutrino mass, 〈 m ν〉, on the order of 0.1 eV, the NEMO 3 double beta (ββ(0ν)) decay experiment requires precise knowledge and control of the backgrounds. The effect of neutrons and γ-rays from the Fréjus underground laboratory (LSM, Laboratoire Souterrain de Modane) has been studied during 10 700 h of data collection. The data were taken with a NEMO 2 prototype detector using different shield configurations. Monte Carlo calculations with GEANT/MICAP code and a new library of γ-rays from neutron captures are presented. The implied consequences for the NEMO 3 detector which is under construction are discussed. The neutrinoless double beta decay background induced by neutrons and γ-rays within the LSM will be suppressed to the very suitable level of 0.1 event in a live time of five years given the appropriate shield and magnetic field.

Double-beta decay with the NEMO experiment: Status of the NEMO 3 detector

The NEMO 3 detector, devoted to search for the neutrinoless double-beta decay, will be able to reach the sensitivity to 〈mν〉 of the order of 0.1 eV. The expected performance of the detector for signal detection and both internal and external background rejection is presented. A specific study of the neutron-induced background is given. The NEMO Collaboration is now mounting the detector in the Frejus underground laboratory.

Double beta decay with the NEMO experiment: status of the NEMO 3 detector

The NEMO 3 detector, now mounting in the Fréjus underground laboratory, is devoted to search for neutrinoless double beta decay and will be able to reach the sensitivity to the effective neutrino mass (< m ν >) in the order of 0.1 eV. The expected performance of the detector for signal detection and both internal and external background rejections are presented. A specific study of the neutron induced background is given.

Results from the NEMO experiment

The NEMO collaboration is building a detector to search for neutrinoless double beta decay. The main results of the second prototype NEMO 2 are presented as well as the expected performance of the final detector NEMO 3.

Double-β decays with the NEMO experiment: final results of NEMO-2 with various nuclei and status of NEMO-3

The NEMO-2 prototype, built for background measurements and located in the Fréjus Underground Laboratory (4800 m w.e.) has provided results with three ββ decay sources, 100Mo, 116Cd and 82Se with data accumulated over a total of 23000 h. Final results of ββ2ν half-lives measurements and limits on 0ν modes are given here. The NEMO-3 detector which will be able to accomodate sources of 10 kg is now under construction. The aim of the experiment is to reach a half-life measurement of ∼ 10 25 y for ββ0ν decay, which corresponds to a Majorana neutrino mass of ∼ 0.1 e V for 100Mo.

NEMO experiment on double beta decay of 100Mo. Present status and future

Background studies have been carried out with the NEMO 2 detector in the search for double beta decay of 100Mo. The low level of background in the 2e channel endorses the proposal of a new tracking detector NEMO 3 to investigate the neutrino mass region [0.1–1.0] eV.