R. Smida, F. Werner, R. Engel, J. C. Arteaga-Velazquez, K. Bekk, M. Bertaina, J. Bluemer, H. Bozdog, I. M. Brancus, A. Chiavassa, F. Cossavella, F. Di Pierro, P. Doll, B. Fuchs, D. Fuhrmann, C. Grupen, A. Haungs, D. Heck, J. R. Hoerandel, D. Huber, T. Huege, K. -H. Kampert, D. Kang, H. Klages, M. Kleifges, O. Kroemer, K. Link, P. Luczak, M. Ludwig, H. J. Mathes, H. J. Mayer, S. Mathys, M. Melissas, C. Morello, P. Neunteufel, J. Oehlschlaeger, N. Palmieri, J. Pekala, T. Pierog, J. Rautenberg, H. Rebel, M. Riegel, M. Roth, F. Salamida, H. Schieler, S. Schoo, F. G. Schroeder, O. Sima, J. Stasielak, G. Toma, G. C. Trinchero, M. Unger, M. Weber, A. Weindl, H. Wilczynski, M. Will, J. Wochele, J. Zabierowski
We report on the first direct measurement of the basic features of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the CROME (Cosmic-Ray Observation via Microwave Emission) experiment have been read out and searched for signatures of radio emission by high-energy air showers. Microwave signals have been detected for more than 30 showers with energies above $3\times10^{16}$\,eV. The observations presented in this Letter are consistent with a mainly forward-beamed, coherent and polarised emission process in the GHz frequency range. An isotropic, unpolarised radiation is disfavoured as the dominant emission model. The measurements show that microwave radiation offers a new means of studying air showers at very high energy.
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http://arxiv.org/abs/1306.6738
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