28 October 2024 – The latest sea campaigns at both the KM3NeT’s ARCA and ORCA sites have led to major progress in expanding detector installations and improving calibration systems.
The number of detection units in operation in the deep sea has been increased to 57: 33 in ARCA and 24 in ORCA.
Despite bad weather at the ARCA site, the so-called Phase-1 part of the apparatus was completed, while construction of Phase-2 was started with the installation of two new junction boxes, three detection units (exploiting a new data acquisition architecture), and calibration components. The operations also included important maintenance tasks, such as recovering and replacing acoustic beacons. All optical modules of the deployed strings are fully operational. KM3NeT/ARCA now comprises 33 detection units.
At the ORCA site, a 60-hour calm weather window allowed the team to deploy the Calibration Unit (Calibration Base+Instrumentation Unit) and to install an additional detection unit. After these successful installations, node 1 of ORCA is complete and fully functional, an important milestone in the construction of ORCA. The total number of functional detection units at ORCA has now reached 24.
These recent efforts at both sites underscore KM3NeT’s expanding capability in detecting and studying neutrinos from the sea’s depths. The whole Collaboration extends its gratitude to the offshore and onshore teams whose hard work made these successful operations possible.
A furled detection unit ready for the deployment at the ORCA siteORCA offshore team on the Castor 02 shipComponents for ARCA on the deck of the Optimus Prime ship: in the foreground is one junction box, behind it there are a couple of spools with the submarine interlink cables and then some detection unitsARCA onshore shift crew at the site of Portopalo
ATLAS comet visible from the harbour of Portopalo di Capo Passero
Sonar scan of the ORCA site taken by the ROV at the end of the operation. The anchors of the detections Units (DUs), the junction box (JB1), the Calibration Base (CB), the Instrumentation Unit (IU) and the Module Instrumentation Interface (MII) are all visible.
13 August 2024 – Gamma-ray bursts are promising candidate sources of high-energy astrophysical neutrinos. The recent GRB 221009A event, identified as the brightest gamma-ray burst ever detected, provides a unique opportunity to investigate hadronic emissions involving neutrinos.
KM3NeT participated in the worldwide follow-up effort triggered by the GRB 221009A event, searching for neutrino events.
In a paper with the title ‘Search for neutrino emission from GRB 221009A using the KM3NeT ARCA and ORCA detectors’ we summarise subsequent searches in the energy range from MeV up to a few PeVs.
We did not find neutrino events, but set upper limits on the neutrino emission associated with GRB 221009A.
90% CL upper limits on the neutrino flux from GRB 221009A for ARCA (blue) and ORCA (red). For comparison the results of IceCube are also shown (green) as well as the gamma-ray observations of Fermi-GBM, Fermi-LAT, and LHAASO (gray dashed lines).
