Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

A Aab, Universität Siegen, Fachbereich 7 Physik - Experimentelle Teilchenphysik, Siegen, Germany.
P Abreu, Laboratório de Instrumentação e Física Experimental de Partículas - LIP and Instituto Superior Técnico - IST, Universidade de Lisboa - UL, Lisboa, Portugal.
M Aglietta, Osservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, Italy.
E J. Ahn, Fermilab, Batavia, Illinois, USA.
I Al Samarai, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris 11, CNRS-IN2P3, Orsay, France.
I F. Albuquerque, Universidade de São Paulo, Instituto de Física, São Paulo, São Paulo, Brazil.
I Allekotte, Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, Argentina.
P Allison, Ohio State University, Columbus, Ohio, USA.
A Almela, Universidad Tecnológica Nacional - Facultad Regional Buenos Aires, Buenos Aires, Argentina.
J Alvarez Castillo, Universidad Nacional Autónoma de México, México, Distrito Federal, Mexico.
J Alvarez-Muñiz, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
R Alves Batista, Universität Hamburg, II. Institut für Theoretische Physik, Hamburg, Germany.
M Ambrosio, Università di Napoli "Federico II" and Sezione INFN, Napoli, Italy.
A Aminaei, IMAPP, Radboud University Nijmegen, Nijmegen, Netherlands.
G A. Anastasi, Università di Catania and Sezione INFN, Catania, Italy.
L Anchordoqui, Department of Physics and Astronomy, Lehman College, City University of New York, Bronx, New York, USA.
S Andringa, Laboratório de Instrumentação e Física Experimental de Partículas - LIP and Instituto Superior Técnico - IST, Universidade de Lisboa - UL, Lisboa, Portugal.
C Aramo, Università di Napoli "Federico II" and Sezione INFN, Napoli, Italy.
F Arqueros, Universidad Complutense de Madrid, Madrid, Spain.
N Arsene, University of Bucharest, Physics Department, Bucharest, Romania.
H Asorey, Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, Argentina.
P Assis, Laboratório de Instrumentação e Física Experimental de Partículas - LIP and Instituto Superior Técnico - IST, Universidade de Lisboa - UL, Lisboa, Portugal.
J Aublin, Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Universités Paris 6 et Paris 7, CNRS-IN2P3, Paris, France.
G Avila, Observatorio Pierre Auger and Comisión Nacional de Energía Atómica, Malargüe, Argentina.
N Awal, New York University, New York, New York, USA.
A M. Badescu, University Politehnica of Bucharest, Bucharest, Romania.
C Baus, Karlsruhe Institute of Technology, Institut für Experimentelle Kernphysik (IEKP), Karlsruhe, Germany.
J J. Beatty, Ohio State University, Columbus, Ohio, USA.
K H. Becker, Bergische Universität Wuppertal, Fachbereich C - Physik, Wuppertal, Germany.
J A. Bellido, University of Adelaide, Adelaide, South Australia, Australia.
C Berat, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Grenoble-Alpes, CNRS/IN2P3, Grenoble, France.
M E. Bertaina, Osservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, Italy.
X Bertou, Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, Argentina.

Abstract

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8±0.7(stat)±6.7(syst) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.