Page 19 - Tlahuizcalli CB-30_Neat

Once again a non-constant background was expected for a massive particle produced by
identified and subtracted from the data. The final cosmic rays in the upper atmosphere
distribution in the time interval from 12 to 21 is
shown in fig. (23). IV. Discussion

A. Muon’s mean lifetime

The results were initially affected by the presence of
a background in the distribution of the decay times
for the muons detected. The photomultiplier had
been calibrated to an optimal operating voltage,
so that the signals produced by the muons were
clearly distinguished. In addition to this, the signals
were sent through a discriminator where a
threshold was set, establishing a lower bound for
the pulses that were observed. These factors lead
to believe that the origin of the background may
not be the electronic noise produced by the
experimental setup. However, there’s always the
possibility that some unexpected noise could be
Figure 23. Time distribution for = 100 after introduced in any part of the circuit.
2
background subtraction.
Once the background was considered, the values
After the gaussian curve fit was carried out, the = 2.429 ± 0.112 , for a PMT voltage of

curve shown in fig. (24) was obtained, with mean 2.00kV and = 2.458 ± 0.113 . The value

value of = 17.768 , and standard deviation reported in the latest Review of Particle Physics is
2
= 0.897 . = 2.1969811 ± 0.0000022 . This value lies

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within the range of 3 (measured in this
experiment) from the ones reported here usually 2
values must differ by more than 3 to be
considered "not equal". Therefore, it can be said
that measurements are consistent with the value
reported by the Review of Particle Physics within a
3 range.

It is also worth mentioning some of the conditions
under which the measurements were performed.
The scintillator was placed in a laboratory located
in the ground floor of a building. Meaning that
muons coming from the atmosphere had to go
across several layers of concrete before arriving to
the detector. This could have affected the lifetime
of muons that arrived to the scintillator, as they had
Figure 24. Gaussian curve fit for the = 100 interacted with different kinds of matter before their
2
distribution. decay times could be measured; this also affected
the amount of muons that arrived to the scintillator,
Given the two mean values for the time as some of them, with low energies, could have
measurements of 2 different separations of the been stopped by the building. One way the
detectors, the mean speed of the muons realization of this technique could be improved, is
according to eq. (12) was calculated to be = by placing the detector in an open space, away
2.400 × 10 ± 1.47 × 10 / . The calculated speed is from buildings that could affect muons. This would
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close but less than the speed of light, which is also improve the amount of muons that can be

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Año 10 Núm. 30 septiembre-diciembre 2024 Tlahuizcalli ISSN: 2448-7260