Status of the KM3NeT project

The KM3NeT Collaboration is constructing a research infrastructure hosting a next generation underwater neutrino observatory in the Mediterranean Sea. It will be a distributed infrastructure with two nodes: ORCA (Mton scale 2500 depth offshore Toulon (France)) and ARCA (Gton scale, 3500 m offshore Capo Passero (Italy)). The ORCA detector, optimised to detect neutrinos of tens of GeV, aims at determining the neutrino mass hierarchy. ARCA is the high-energy component and is dedicated to the search for extraterrestrial neutrino sources in the TeV-PeV range. The KM3NeT Collaboration has started the construction of both detectors. The first detection units were deployed and the data analysis is ongoing to validate the detector performances. In this paper we give a general overview of the two detectors. We also report the present status of the detector and the first results of data analysis.

THE CHARACTERISTICS OF GRBs WITH PRESENCE OF HIGH ENERGY COMPONENT IN THEIR SPECTRA

The properties of GRBs with presence of high energy emission in spectra are discussed. The temporal profiles of part of events are similar in various energy bands in prompt phase (as for GRB 080528, GRB 021008) but during some events extended high energy emission was detected (for example, GRB 090902B). For other part of GRBs temporal profiles are quite different in various energy bands during prompt phase (as for GRB 050525B), but for some such events extended high energy emission was observed too – for example, GRB 080514B. Moreover, high energy precursors were registered for several GRBs: some photons in energy band 30 MeV - 30 GeV were detected by AGILE during GRB 080514B. The shape of energy spectra of GRBs with presence of high energy emission can follows the Band model (or power law or broken power law) up to some tens or hundreds of MeV (as for GRB 021008) or contains additional high energy power law component (for example, GRB 050525B and GRB 090902B). Following this criteria it is possible to separate two main subclasses of GRBs with high energy emission. Both types of GRBs observed since CGRO mission beginning. The analysis of their energy spectra has shown that the break between additional high energy component and Band (or power law or broken power law) component was in energy region 2-200 MeV. Both types can have got extended high energy emission including component with E > 500 MeV for some events and low energy precursors. The special features of second class of GRBs by the results of preliminary data analysis are the absence of hard to soft evolution in the low energy band and (or) presence of the high energy precursors for some events.