KM3NeT - News Archive

Archive of news items

New publication: Neutrino Mass Ordering and Oscillation Parameters

05 May 2021 – The potential of KM3NeT to measure key properties of neutrinos – in March 2021, the KM3NeT Collaboration released a publication showing that  KM3NeT with its ORCA detector will be in an excellent position to study the phenomenon of neutrino oscillations!

Three neutrino flavours and oscillation

Neutrinos come in three species called flavours: the electron neutrino, the muon neutrino, and the tau neutrino. In the 1960’s, the first experiment was started to study the sun by measuring the flux of electron neutrinos that the solar nuclear processes copiously produce. The experiment revealed that the flux was inconsistent with the expectations! Many solutions were put forward to explain the discrepancy until a measurement of the flux of neutrinos of all three flavours was made and found compatible with the expectation. This key measurement meant that the expectations for the neutrino flux produced by the sun were correct and that the electron neutrinos were converted into other flavours while traveling to Earth. This phenomenon is called neutrino oscillation, subsequently detected also in other contexts. This phenomenon is only explained by quantum mechanics and requires that the neutrinos, initially thought massless, are actually massive!

Neutrino admixture

The neutrinos with definite masses happen to be different from the neutrinos with definite flavours. In other words, a neutrino of a given flavour is an admixture of the neutrinos of definite mass as shown in the top part of fig:1. Because of the mass difference between the neutrino mass states, these states do not propagate at the same velocity. As a result, the neutrino admixture evolves during the propagation, as shown in the bottom part of fig:1. In other words, while propagating, the neutrino flavour changes.

 

Figure 1: Top:the mass state admixtures corresponding to the flavour (so-called weak) states for 2 neutrinos. Middle: a muon neutrino is produced at t=0. As time goes, the neutrino mixture varies reaching periodically a pure muon neutrino state. The probability for the neutrino to be detected in each flavour is represented at the bottom. Reproduced from Slansky et al. Los Alamos Sci. 25 (1997) pp. 28-63.

Using atmospheric neutrinos

The KM3NeT Collaboration aims to study this oscillation phenomenon using neutrinos produced in the collisions of cosmic rays onto the atmosphere. Using these neutrinos, the KM3NeT Collaboration will be able to measure one of the key parameters ruling the neutrino admixture: the so-called θ23 mixing angle. We will also be able to measure the squared mass difference between two of the neutrino mass states – δm232 – and to tell which of the three mass states is the heaviest, i.e. determining the neutrino mass ordering as shown in fig:2. Finally, we will check if the standard three neutrino oscillation paradigm is valid by measuring the fraction of cosmic-ray induced neutrinos that have oscillated to the tau neutrino.

Figure 2: Sensitivity to neutrino mass ordering as a function of data taking time for both normal (red upward pointing triangles) and inverted ordering (blue downward pointing triangles). See the paper for more details and the values of the oscillation parameters considered to obtain the result.

Unique potential

The publication relies on precise simulations to determine the sensitivity of the KM3NeT/ORCA detector to these parameters. The prospects show that the experiment has a unique ability to make these measurements and that world best results can be obtained in few years of data taking with the full detector.

The publication has been submitted to EPJ-C and is available as a pre-print as arXiv:2103.09885.

 

Exciting deployment on the ARCA site!

15 April 2021 – During the last few weeks – despite the pandemic – the KM3NeT Collaboration worked hard to make five new detection units for ARCA ready for deployment. Spooled on their launching vehicles they arrived at the harbour of Malta where a team of KM3NeT technicians, engineers, and scientists inspected thoroughly the units for the last time before they were loaded onto the Miss Marilene Tide of the FUGRO company. In the early morning of 8th April the ship sailed out toward the IDMAR site of ARCA near Sicily for an amazing sea operation. After installing several new components for the seafloor network, on Monday 12 April the deployment of the five new detection units began.

Press_release_ARCA_042021 (pdf)

 

Detection unit approaching touch down at the seabed, 3500 m deep.

 

Junction box at the seabed with the plugs of five detection units.

 

Located in the Mediterranean Sea at a depth of 3,500 m about 80 km offshore Capo Passero, Sicily, the ARCA telescope together with its sister telescope ORCA, located offshore Toulon, France will allow scientists to identify the sources of high-energy cosmic neutrinos emanating from cataclysmic events in the Universe and to study the fundamental properties of the elusive neutrino.

Once complete, the KM3NeT/ARCA detector will form an array of more than two hundred detection units. Each of the 700 m tall units comprises 18 optical modules equipped with ultra-sensitive light sensors that register the faint flashes of light generated by neutrino interactions in the pitch-black abyss of the Mediterranean Sea.

The journey of our new detection units started earlier this month where, after being assembled and prepared for deployment, they left the labs in Catania and Naples on the ferry for Malta. The detection units represent the output of a construction effort distributed over many institutes of the Collaboration.

It took only two days to deploy, test and connect the five new units to the seafloor network. They add to the first detection unit of the apparatus, deployed as early as 2015. In the control room in Capo Passero the first data after connection were recorded immediately. An amazing sea operation came thus to an end, marking a big step for KM3NeT, which is operating now with six detection units in ARCA and also six at ORCA. KM3NeT is now ready to sustain mass construction of the apparatuses at the two sites.

Stay tuned: next sea campaigns for ARCA and ORCA are planned in a few months!

 

The five detection units of KM3NeT onboard the deployment ship.

 

Control of the operation from the shore laboratory in Portopalo di Capo Passero (the operation was performed in full respect of the anti-COVID-19 safety measures).

 

 

Enjoy the videos of the sea operation at our KM3NeTneutrino YouTube channel

 

KM3NeTneutrino Youtube channel:

Overboarding of the junction box (aerial view):

Overboarding of a detection unit:

Contact:

Exciting times for neutrino astronomy!

15 March 2021 – In the past weeks, not one but two exciting observations were published in the field of neutrino-astronomy! A neutrino was observed that could be correlated to a Tidal Disruption Event observed by the Zwicky Transient Facility and for the first time a particle shower was observed by the IceCube detector at the energy of the Glashow resonance. KM3NeT rejoices for these remarkable observations that show the increasing power of neutrino astronomy and multi-messenger observation.

A high-energy neutrino detected in the direction of a Tidal Disruption Event

The IceCube Neutrino Observatory constantly monitors the sky, searching for high-energy neutrinos emitted from the most energetic phenomena in our Universe. When they find one, they send an alert to the astronomy community, hoping other instruments could also see an electromagnetic signal from the same location in the sky.

In October 2019, the Zwicky Transient Facility observed, in the direction of one of these neutrino alerts, the signal expected from a Tidal Disruption Event, the shredding of a star coming close from a black hole. The probability of having a high-energy neutrino correlated with this astrophysical event, named AT2019dsg, by chance has been determined to be of 0.2% by the team leading the research project at DESY, Germany.

This electromagnetic radiation – neutrino correlation might be the first one from this source population. More data, and hopefully more correlated observations, are needed to fully characterise the phenomenon. Our colleagues in the Mediterranean Sea, the ANTARES Collaboration, have also searched for neutrinos from AT2019dsg.

KM3NeT will be a tremendous asset in this quest.  Our realtime multi-messenger astronomy program will allow us to send an alert when an interesting neutrino candidate is detected in KM3NeT but also respond to alerts sent by partners detecting electromagnetic or gravitational waves.

More info on the TDE-neutrino association:

 

After the supermassive black hole tore the star apart, roughly half of the star debris was flung back out into space, while the remainder formed a glowing accretion disc around the black hole. Credit: DESY, Science Communication Lab

A particle shower detected at the Glashow resonance

The IceCube Collaboration has reported the first observation of a particle shower at the energy of the Glashow resonance. This process, predicted 60 years ago by S. Glashow, occurs when an electron anti-neutrino interacts with an electron. At a very high energy (6.3 PeV), there is a resonance effect and the interaction probability for this anti-neutrino is 300 times larger than that of the other neutrino flavours at the same energy.

The process only happens for an electron anti-neutrino, and does not for the electron neutrino or the other neutrino flavours. This process therefore gives the possibility to probe the content of the high-energy astrophysical flux of neutrinos and constrain the mechanism that has produced them at the source. Indeed, depending on the production channel (for example whether accelerated protons interact with matter or with light) we will expect a different ratio of neutrino vs anti-neutrino. With only one event, we cannot yet differentiate between the possible production models.

The KM3NeT/ARCA detector in KM3NeT will be sensitive in this energy range and will contribute to hopefully detect more of these Glashow resonance events. With more data, we will be able to use these events to better understand the processes occurring in the most energetic phenomena in our Universe.

Read the ins and outs of the result in the associated Nature news and views written by Carla Distefano, member of the KM3NeT Collaboration: https://www.nature.com/articles/d41586-021-00486-1

For detailed info on the Glashow resonance event found by IceCube and the performance expected of KM3NeT:

A visualisation of the Glashow event recorded by the IceCube detector. Each colored circle shows an IceCube sensor that was triggered by the event; red circles indicate sensors triggered earlier in time, and green-blue circles indicate sensors triggered later.

 

(Credit feature image: IceCube Collaboration (ICL photo by Yuya Makino, IceCube/NSF))

 

New publication:  core-collapse supernova explosions

11 March 2021 – In February 2021, the KM3NeT Collaboration released a publication describing the potential of KM3NeT to detect low-energy neutrinos from a future core-collapse supernova. The publication is submitted to the European Physical Journal  C.

What is a core-collapse supernova?

Core-collapse supernovae  are very energetic explosions that can end the life of massive stars. They have the peculiar feature of releasing about 99% of their energy as a huge flux of low-energy neutrinos. The neutrinos can escape the stellar core carrying information on the physical processes at play in the collapse, when the star is still opaque to light.

How well can KM3NeT observe a core-collapse supernova?

Thanks to the technology of KM3NeT based on the multifaceted modules with light sensors the KM3NeT detectors are particularly sensitive to the low-energy neutrinos from a supernova.  In the publication it is shown that KM3NeT  – when finished building the detectors –  can reach a 5 sigma discovery potential to observe a core-collapse supernova happening in the Milky Way. For the most optimistic theoretical models describing core-collapse supernovae, the detection threshold can extend up to the Large Magellanic Cloud.

The potential sensitivity of the KM3NeT detectors with 230 detection units in the ARCA detector and 115 units in the ORCA detector as a function of distance of the core-collapsed supernova. Curves are shown for three different masses of the progenitors.

Details

Once a core-collapsed supernova is observed, researchers of KM3NeT can study aspects of the neutrino emission such as the detected neutrino light curve and the neutrino spectrum. This will provide the potential for discrimination between different theoretical models of core-collapse supernovae and help to understand the physical processes behind the explosion mechanism. The time of arrival of the neutrino signal can be determined with an accuracy better than 10 ms for a source at the Galactic Center. The oscillating signature of hydrodynamical instabilities and other physical processes impacting the neutrino time profile can also be detected for nearby events: 3 sigma at 3-8 kpc, depending on the model. From the recorded coincidences, KM3NeT will be able to infer the properties of the neutrino spectrum, estimating the mean neutrino energy with a precision of about 2% if the other spectral parameters such as the energy scale and pinching parameter are known with a small uncertainty.

Neutrino light curves expected using the future full ARCA detector of 230 detection units, from a core-collapse supernova at a distance of 5 kpc and a progenitor of 27 solar masses.

What is possible with the current six detection units of the ORCA detector?

Already with the six detection units of the ORCA detector currently taking data, a detection at 5 sigma level of a core-collapse supernova can be achieved for supernovae at distances up to 10 kpc. The online analysis pipeline is in place, sending warning messages to SNEWS  – the worldwide network  for early warning for supernova events. The first MeV neutrino follow-ups of warnings by gravitational-wave detectors were performed using the data of only four ORCA detection detection units  that were active at that time, bringing the first KM3NeT physics results.

 

Exciting times are ahead. KM3NeT is ready for the observation of the next core-collapse supernova event in our Galaxy!

A collaboration in corona times

18 February 2021 – Like everyone else the KM3NeT Collaboration has to follow the restrictive measures against the COVID-19 pandemic. So, once more, the last two weeks we held our Collaboration meeting on-line. At this virtual meeting we discussed the many details of building the telescopes, analysing the data and developing the simulation programs.  We are very encouraged by the large progress with constructing the many detector components and the installation of the ARCA and ORCA telescope infrastructures. We are excited by the many analyses of data from the installed detector units on which we will  report at the upcoming conferences. Nevertheless, we  tremendously miss our colleagues.  In particular, for the young scientists in our Collaboration these are difficult times, but they are amazing in their efforts for the Collaboration.

During the Collaboration meeting we virtually said goodbye and thank you to Marco Anghinolfi, who will be retiring soon after many years of service to the Collaboration.  We hope you enjoy your retirement. Arrivederci, but no goodbye!

We virtually raised a glass to thank Mauro Taiuti for his four years of leadership as Spokesperson of KM3NeT. Fortunately, he has promised to continue his scientific career in the Collaboration!

We are looking forward to the new leadership of Paschal Coyle and his team. All the best for executing the tremendous task ahead of building the telescopes and executing the scientific program – also in corona times. We will do our best to support you!

We virtually applauded our PhD students who have recently completed their theses and wished our postdocs leaving the Collaboration all the best for their careers!

We virtually welcomed new students and postdocs who will work on the nitty gritty of data analysis and detector calibration. We hope to meet you face-to-face very soon!

Last but not least, we  virtually welcomed LPC Caen, France as a new group in the collaboration who  will participate in both the construction work and the scientific program. Super!

On the bright side of virtual meetings our conference committee reported a more diverse participation of our Collaboration in the international conferences. More people took part and the representation among speakers was better balanced in seniority and gender.

Building and operating a telescope is an attractive, tremendous, collaborative effort relying on  a lot of human interaction, hard to recreate in a virtual environment – but we did our best! We were still able to generate our customary  Collaboration group picture as you can see below: a collaboration in corona times.

 

 

Upgrade of ARCA infrastructure

21 December 2020 – Just in time for the winter break, a nice Christmas present was delivered to KM3NeT:  the second main cable between the ARCA detector site and the shore station in the lovely village of Porto Palo di Capo Passero at the isle of Sicily, Italy has been installed. It is an important step in the program of upgrading the ARCA seafloor network for the ARCA detector near Sicily, Italy.

Read more

‘Draw me a neutrino’

13 December 2020 – Have a look at the banner pictures of the KM3NeT home page. During December 2020 and January 2021, we display amazing drawings of the three neutrino-flavours: muon-neutrinos, electron-neutrinos and tau-neutrinos.

The drawings are made by the winners of the KM3NeT contest ‘Draw me a neutrino‘. We invited everyone from young to old to use their imagination and picture a neutrino.

 

About 500 people from Ecuador, France, Georgia, Greece, India, Italy, Morocco, Netherlands, Switzerland, Russian Federation, Spain and the UK took up the challenge.

The best drawings are now on display in an online exhibition in our Virtual Neutrino Art Centre (hub.link/ZZwzhf7).

You can find the drawings and the names of their authors here.

And a high resolution version of the drawings .

 

Enjoy!

New paper: Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling

20 November 2020 – The KM3NeT Collaboration has published a new paper, in which we describe in detail the innovative deployment method for KM3NeT detection units.

No standard moorings

A custom design was necessary, because the KM3NeT mooring – the detection unit -is different from moorings typically used for oceanography.

For instance, in KM3NeT moorings the instrumentation is contained in transparent and thus unprotected glass spheres. That makes them vulnerable during deployment. Moreover, we use a long, thin and soft tube with optical fibres and thin copper wires for data transmission and electrical power for the instruments. That makes the units even more vulnerable.

On top of that, because we use thin Dyneema ropes as strength members in stead of a standard steel cable the mooring is not strong enough to carry the weight of the anchor during deployment.

All this makes it more difficult to deploy the unit without breaking it and we needed a customised deployment method.

Different from other telescopes

Compared to other neutrino telescopes such as ANTARES in the Mediterranean Sea and GVD in Lake Baikal, we designed the KM3NeT detection unit even more slender to minimise the amount of material used for support of the sensor modules. An other – economical – difference is that we have to deploy hundreds of units more for KM3NeT in a period of a few years while keeping the costs for sea operations at a minimum. These are even more reasons for innovation of the deployment method.

The LOM

We developed a custom-made, fast deployment method. Despite the length of the detection unit of several hundreds of metres, we managed to compact it into a small, re-usable spherical launching vehicle instead of deploying it weight down from a surface vessel – the standard method in oceanography. We dubbed the vehicle LOM for Launcher of Optical Modules.

The tric

Once the LOM has reached the seafloor, the innovative tric begins. The buoyant LOM rolls upwards along the Dyneema ropes. While doing so, it spits out the glass spheres with instrumentation attached to the ropes. As a result, while floating to the surface, the LOM leaves the detection unit behind at the seabed, unfurled to its full vertical length. Ready for data taking during many years to come.

Cost effective

The LOM has two economical advantages. First, it does not take a lot in space. Therefore, during a sea operation many LOMs can be stored on deck of a ship. Secondly, we can lower the LOM to the seabed at high speed. As a result, we need less expensive ship time for the installation of the KM3NeT telescope.

Cooperation

As far as we know, the method of compact deployment of moorings with a LOM is unique. The method is the result of close cooperation between engineers and scientists in the KM3NeT Collaboration from both oceanographic and astrophysics institutes. We hope it will inspire oceanographic scientists for the design and deployment of their future moorings.

Details

In the paper, we describe the details of the design of the LOM, the loading with a detection unit, and its underwater self-unrolling. You find the reference below.

LOM in pictures

Pictures below reflect the  process from idea to realisation. First an impression of the initial ideas for deployment by @Marijn van der Meer/Quest. Followed by the technical design of the KM3NeT detection units that must be installed and the design of the LOM launcher vehicle. Finally, photos of the first prototype of the LOM and the final version that is now regularly used for the installation of the detection units of the ARCA and ORCA detectors of the KM3NeT telescope.

 


 

Reference

Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling

The KM3NeT Collaboration: S. Aiello et al 

2020 JINST 15 P11027

https://doi.org/10.1088/1748-0221/15/11/P11027