1. Measurement of the Atmospheric Muon Charge Ratio by Using a Cosmic Ray Telescope
Soheila Abdollahi
(Imam Khomeini International University, Sharif University of Technology)
Tehran, Iran
ICRC 2011, Beijing

2. Outline Cosmic ray telescope Importance of Muon charge ratio
The muon charge ratio
Simulation
Conclusions
November 11, 2018
32nd ICRC, Beijing, China

3. Cosmic Ray Telescope
Consists of 2 plastic scintillator modules (30×10×1cm3) with spacing 1m from each other
It’s placed in the floor4 of Physics Department of Sharif University of Technology, under 80 cm concrete in Tehran (35º43´N, 51º20´E)
1200m above sea level (890gcmˉ²)
Telescope is a rotatable device around its vertical axis in different zenith and azimuth angles
November 11, 2018
32nd ICRC, Beijing, China

4. Importance of muon charge ratio
Useful information about neutrino oscillation
T. K. Gaisser and T. Stanev, Phys. Rev. D 38, 85 (1998)
M. Honda et al., Phys. Rev. D 52, 4985 (1995)
Distinguish between Hadronic and leptonic showers
Comparing with Monte Carlo simulations results
J. Wentz et al., Phys. Rev. D 67, (2003)
I. M. Brancus et al, Proc. 27th ICRC, Hamburg, Germany , 1187 (2001)
November 11, 2018
November 11, 2018
32nd ICRC, Beijing, China
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

5. The muon charge ratio
we measured the muon charge ratio (Rμ) with delayed coincidence method based on different interactions of positive and negative muons with matter.
While positive muons decay in matter with life time of free muon, the negative muon is captured by the host atom and forming a muonic atom.
Nuclear capture rate is proportional to Z4, that Z is atomic number of absorber material.
Medium
Mean Life Time (ns)
Decay Probability (%)
vacuum
±0.04
100.00
Carbon
2026.3±1.5
92.15
Oxygen
1795.4±2
81.57
Aluminum
864.0±1
39.05
Silicon
756.0±1
34.14
Lead
75.4±1
2.75
T. Suzuki and D. F. Measday and J. P. Roalsvig, Phys. Rev. C53, 2212 (1987)
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

6. τμ+ and τμ- are life time of positive and negative muon.
Total muons decay distribution function in scintillator is including superposition of several decays as follows:
τμ+ and τμ- are life time of positive and negative muon.
τbg stands for time constant of background radiation.
Pdecay is decay probability of negative muon in Scintillator.
But τbg …
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

7. Determining the Time constant of bg radiation
The average time constant of bg radiation (τbg) was calculated ns.
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

8. Soheila Abdollahi, IKIU
Average muon charge ratio was obtained 1.15±0.03 in one week time intervals.
The values of muon charge ratio in different time intervals, show the fluctuations are very small and for three-week time interval and more, the values of Rµ tend to a fixed amount 1.18±0.02.
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

9. Our result in comparison with others
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

10. Simulation We simulated the extensive air showers with CORSIKA code
In energy range from 1012 eV to 1016 eV
primary particles (proton and helium)
we used one high energy model (QGSJET) and two low energy models (UrQMD and GHEISHA)
We selected muons with:
energy between 0.76 GeV to 1.6 GeV which is near to energy range of telescope.
Zenith angle Ꮎ≤ 9°
we obtained in the model of
QGSJET - GHEISHA, Rμ= 1.06±0.10
and in the model QGSJET - UrQMD, Rμ= 1.04±0.17.
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

11. Conclusions
we estimated time constant of background radiation, ns.
We estimated Rµ = 1.15±0.03 in one week time interval.
for three-week time interval and more, Rµ tend to a fixed amount 1.18±0.02.
Obtained Rµ = 1.06±0.10 in QGSJET-GHEISHA models and 1.04±0.17 in QGSJET-URQMD models.
By increasing the number of simulated showers, the results could be improved.
November 11, 2018
32nd ICRC, Beijing, China
Soheila Abdollahi, IKIU

12. Thank you