Lateral Distribution of Cosmic Ray Muons
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Date
2025-10
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Kenyatta University
Abstract
Cosmic rays are high-energy particles that travel through space at nearly the speed of
light. Primary cosmic rays originate from sources such as the sun, supernovae, black
holes, and active galactic nuclei. When these primary cosmic rays interact with the
Earth's atmosphere, they produce secondary cosmic rays, including cosmic ray muons,
which are a significant component that reaches the Earth's surface. The lateral
distribution of cosmic ray muons is a key factor in understanding the elemental
composition of primary cosmic rays and the development of extensive air showers in
the atmosphere. The aim of this work was to estimate the elemental composition and
interaction of primary cosmic rays in the atmosphere. Two NaI(Tl) detectors and
associated electronics were used to carry out the measurements. The detectors were
separated at regular intervals ranging from 0 to 30 meters. Cosmic ray muons were
detected by the NaI(Tl) detectors. For each detector separation, the number of
coincident muons and the total number of detected muons were recorded at two-hour
intervals. The experiment was conducted at Kenyatta University during the months of
March, April, and May 2019.The data collected were analyzed, and a decoherence
curve was plotted, showing the number of counts per minute as a function of the
separation distance between the detectors. The coincidence rate was fitted using the
Nishimura-Kamata-Greisen (NKG) function and compared with Monte Carlo (MC)
simulations of extensive air showers. The simulation were based on the DPMJET-III
model, and the simulated results agree well with experimental data. The analysis of the
experimental data revealed a primary cosmic ray composition of (86 ± 3)% protons, (10
± 31)% helium, and (4 ± 3)% iron. These results for protons and iron are consistent with
other reported values, while the helium component shows some deviation. This work
contributes to our understanding of the mass composition of primary cosmic rays and
their interaction with the Earth's atmosphere.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Masters of Science (Physics) in the School of Pure and Applied Sciences of Kenyatta University October, 2024
Kenyatta University
Supervisors:
1. Nadir O. Hashim
2. Livingstone Ochilo