Study of “neutron bursts” with Mexico City neutron monitor

A search was made for abnormal high multiplicity neutron events, with the combined array of a 6NM64 neutron supermonitor and eight plastic scintillators installed in México City. Some evidences were presented in the last years for such events [Akad. Nauk, Ser. Fiz. 61 (3) (1997) 486; Nucl. Phys. B (Proc. Suppl.) 75A (1999) 333], but their existence was not established beyond any doubt, nor the conditions under which they occur. Our results show the existence of very high multiplicity events in coincidence with high counting rates of the plastic scintillators during several milliseconds. A detailed consideration of the experiment and data on the multiplicities as well as the temporal distributions of the pulses are presented. We propose that the explanation of the peculiar pulse time distributions in the detectors in such events may be found in neutron physics known processes rather than in delayed extensive air showers (EAS) component phenomena as claimed in [Nucl. Phys. B (Proc. Suppl.) 75A (1999) 333]. On the other hand, the origin of these EAS with very high multiplicity of neutrons is a question that remains unanswered.