The Antarctic Impulsive Transient Antenna (ANITA) detector has observed several radio pulses coming from the surface of the ice cap at the South Pole. These pulses were attributed to upward-going atmospheric particle showers instead of the downward-going showers induced by cosmic rays that exhibit a characteristic polarity inversion of the radio signal due to reflection in the ice. Coherent transition radiation from cosmic-ray showers developing in the atmosphere and intercepting the ice surface has been suggested as a possible and alternative explanation of these so-called "anomalous" events. To test this interpretation, we have developed an extension of ZHS, a program to calculate coherent pulses from electromagnetic showers, to deal with showers that transit a planar interface between two homogeneous and dielectric media, including transition radiation. By considering different geometries, it is found that all pulses from air showers intercepting the ice surface and detected at the height of ANITA, display the same polarity as pulses emitted by ultra-high-energy cosmic-ray showers that fully develop in the atmosphere and are reflected on the ice. We find that transition radiation is disfavored as a possible explanation of the anomalous ANITA events.
Coherent transition radiation from the geomagnetically-induced current in cosmic-ray air showers: Implications for the anomalous events observed by ANITA
Exact spherical-wave forward model for radio reflection from stratified media and implications for the anomalous-polarity events observed by ANITA
Center for Cosmology and AstroParticle Physics (CCAPP), Ohio State University（俄亥俄州立大学宇宙学与天体粒子物理中心）；Department of Physics, Ohio State University（俄亥俄州立大学物理系）；Department of Astronomy, Ohio State University（俄亥俄州立大学天文系）
ICECUBE对高能宇宙中微子的观测开创了超越标准模型探索宇宙和新物理的新纪元。在标准图中，虽然大部分$ν_μ$和$ν_e$是在源中产生的，但振荡将产生$ν_τ$ { \it en route}。某些超越SM的场景，比如与超轻型DM的交互，可以改变这种情况。因此，宇宙中微子流的味道成分可以打开探索某些超出SM场景的可能性，否则是无法进入的。我们表明，$τ$味在中微子味中占有特殊的地位，在阐明新的物理。将ANITA观察到的两个异常事件解释为$ν_τ$事件，使得tau的味道更加有趣。我们研究了如何检测的两个tau事件的ICECUBE约束的中微子与超轻暗物质的相互作用，并讨论了这种相互作用的影响，甚至更高的能量宇宙中微子可探测的未来射电望远镜，如ARA，ARIANNA和GRAND。我们还重新审视了$3+1$中微子计划作为一个解决方案的两个异常ANITA事件，并澄清了一个误解，存在于文献中的高能中微子在物质中的演化的$3+1$计划与散射的可能性核。我们表明，现有的界限上的磁通量的$ν_τ$与EeV的能量排除了这种解决方案的ANITA事件。我们表明，$3+1$解决方案可以保存从这个约束和约束的额外的相对论自由度在早期宇宙中打开的中微子与超轻暗物质的相互作用。
