Neutron Monitors detecting cores of Extensive Air Showers

A. Chilingarian, Artem Alikhanyan National Lab (Yerevan Physics Institute), Yerevan, Armenia

We identify and analyzed EAS events by the registration of the neutron bursts in the Aragats NM. We relate these bursts to the EAS cores hitting the ground nearby NM. All bursts were observed as sequences of microsecond pulses temporally isolated from other pulses on a time scale of at least 100 microseconds. The burst duration, defined as a time interval between the first and last detectable pulses in the sequence was 2.5 ms +/- 0.6. Thus, NM is enlarging the EAS core particle lifetime (usually not more than 20 � 30 ns) by 5 orders of magnitude by registering multiple secondary neutrons born in the lead absorber and soil by relativistic particles from the EAS core. In this way, NM registers EASs and enables the estimation of primary particle energy by measuring the event multiplicity (number of isolated pulses in NM) and relating it to the primary particle energy. Although the sensitive area of NM is only several tens of m2, multiyear operation of the NM network will provide sufficient statistics for the physics around the knee of all particle energy spectrum (3-4 PeV) and beyond. The largest cosmic ray experiments confirm the neutron bursts from EAS cores without any relation to lightning occurrences. The network of near � 50 neutron monitors (NM) operates 24/7 around the globe at different altitudes, latitudes, and longitudes for more than 60 years. Maintenance of such detectors is very cheap and they are providing data for many years with minimal intervention of personnel. The data from neutron monitors are collected in databases with open access and a user-friendly interface. After a very simple modernization of NM electronics, it will be possible to recover the energy spectra of galactic cosmic rays with detectors located all around the globe.