用IceTop测量空气簇射中GeV μ子的密度
Density of GeV muons in air showers measured with IceTop
摘要：
我们提出了一个测量的GeV μ介子的密度在近垂直的空气淋浴使用三年的数据记录的冰顶阵列在南极。根据簇射的大小，μ子密度已被测量在200米和1000米之间的横向距离。从这些横向分布，我们得到的μ介子密度作为能量的函数，在600米和800米的参考距离为2.5 PeV和40 PeV之间的初级能量和9 PeV和120 PeV之间，分别。μ子密度的确定使用，作为基线，强子相互作用模型Sibyll 2.1连同各种组成模型。测量结果与这些基线相互作用和组成模型中预测的μ子密度一致。测得的μ介子密度也进行了比较，模拟使用后LHC模型EPOS-LHC和QGSJet-II.04。这种比较的结果是，后LHC模型与任何给定的组成模型一起产生比观察到的更高的μ子密度。这与1 EeV以上的观测相反，其中所有模型模拟对于任何质量组成都产生比测量的更低的μ子密度。后LHC模型一般具有较高的μ子密度，因此在最高能量下与实验数据的一致性得到改善，但μ子密度在2.5 PeV和约100 PeV之间的能量范围内不正确。
英文摘要：
We present a measurement of the density of GeV muons in near-vertical air showers using three years of data recorded by the IceTop array at the South Pole. Depending on the shower size, the muon densities have been measured at lateral distances between 200 m and 1000 m. From these lateral distributions, we derive the muon densities as functions of energy at reference distances of 600 m and 800 m for primary energies between 2.5 PeV and 40 PeV and between 9 PeV and 120 PeV, respectively. The muon densities are determined using, as a baseline, the hadronic interaction model Sibyll 2.1 together with various composition models. The measurements are consistent with the predicted muon densities within these baseline interaction and composition models. The measured muon densities have also been compared to simulations using the post-LHC models EPOS-LHC and QGSJet-II.04. The result of this comparison is that the post-LHC models together with any given composition model yield higher muon densities than observed. This is in contrast to the observations above 1 EeV where all model simulations yield for any mass composition lower muon densities than the measured ones. The post-LHC models in general feature higher muon densities so that the agreement with experimental data at the highest energies is improved but the muon densities are not correct in the energy range between 2.5 PeV and about 100 PeV.
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