On possible role of neutrons in appearance of delayed muons in MUON-T setup at the Tien Shan high-altitude station

• Published in: Bulletin of the Lebedev Physics Institute Vol. 36; no. 9; pp. 260 - 262
• Main Authors: Vavilov, Yu. N., Dedenko, G. L.
• Format: Journal Article
• Language: English
• Published: Heidelberg Allerton Press, Inc 01-09-2009
• Subjects: Physics; Physics and Astronomy; Neutron Transport; Shower Core; Lebedev Physical Institute; Total Statistic; Soil Depth
• ISSN: 1068-3356; 1934-838X
• DOI: 10.3103/S1068335609090024

The MUON-T setup operated at the Tien Shan high-altitude station of the Lebedev Physical Institute (3340 m above sea level) at a soil depth of ∼10 m (∼20 m m.w.e.). Muons with delay times of 30–150 ns with respect to the extensive air shower front were observed at this setup. Calculations showed that delay times of relativistic muons, taking into account their deviations in the geomagnetic field, do not exceed ∼30 ns. To elucidate the possible role of neutrons in the appearance of delayed events due to the
n-p
reaction in the plastic scintillator material, the problem of neutron transport in a medium with a density of 2 g/cm
3
and a humidity of 10% was solved by the Monte Carlo method. Calculations for a point source of neutrons with energies of 5, 10, and 20 MeV (such neutrons can be generated, in particular, in cascades in soil from hadrons of the shower core) showed that the neutron flux decreases more than by a factor of 10
4
at a distance of 2.8 m of soil from the source. Neither neutron crosses the boundary of 3m at the total statistics of 3 · 10
5
events. Since the MUON-T setup is at a depth of 10 m, it is clear that neutrons from the atmosphere and soil upper layer are absorbed, scattered, and do not reach the detector. Thus, the formation of delayed muons in the MUON-T setup cannot be explained by these neutrons.