Speaker
Description
The modulation effect of cosmic-ray muon flux measured in underground laboratories with atmospheric temperature has been observed in early underground experiments. The muon event rate is positively correlated with atmospheric temperature changes, which can be explained by the related theories of Barrett, Gaisser, and others. However, at the Daya Bay Neutrino Experiment, a nonlinear phenomenon is observed in the study of the data of the shallower Experimental Halls 1 and 2. To understand this phenomenon, we used the MCEq, which is a numerical calculation tool for atmospheric shower cascade equations, to simulate atmospheric showers, deploying real atmospheric and terrain data, and we reproduced the nonlinear effect of muon flux modulation by temperature observed in the Daya Bay experiment. Furthermore, through simulation methods, we ruled out several factors that could cause the nonlinearity, including mountainous terrain effects, changes in the primary cosmic ray energy spectrum, muon energy losses and decay in the atmosphere, and the scale invariance approximation of hadronic cross-sections in atmospheric showers. In terms of theoretical models, we found that the solutions for meson and muon spectra provided by existing theories are only approximate solutions of the original atmospheric shower evolution equations under high energy, low energy, or isothermal atmospheric conditions and when calculating the linear coefficient of muon flux and temperature change, only the local atmospheric temperature variation is considered. We provided exact solutions of the evolution equations, taking into account the influence of long-range atmospheric temperature variations on muon flux, and developed corresponding theoretical models. These numerical simulations and theoretical developments may explain the nonlinear dependence of underground muon flux on atmospheric temperature found at the Daya Bay experiment.
| 请选择分会 | 中微子物理、粒子天体物理与宇宙学 |
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