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

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

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

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, 073020 (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

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 2197.03±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

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

Determining the Time constant of bg radiation The average time constant of bg radiation (τbg) was calculated 284.8 ns. November 11, 2018 32nd ICRC, Beijing, China Soheila Abdollahi, IKIU

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

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

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

Conclusions we estimated time constant of background radiation, 284.8 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

Thank you