R. Hiller

Radio measurements of the energy and the depth of the shower maximum of cosmic-ray air showers by Tunka-Rex

We reconstructed the energy and the position of the shower maximum of air showers with energies E & 100PeV applying a method using radio measurements performed with Tunka-Rex. An event-to-event comparison to air-Cherenkov measurements of the same air showers with the Tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. The Tunka-Rex reconstruction methods and absolute scales have been tuned on CoREAS simulations and yield energy and Xmax values consistent with the Tunka-133 measurements. The results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. The energy precision of Tunka-Rex is comparable to the Tunka-133 precision of 15 %, and exhibits a 20% uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. For Xmax, this is the first direct experimental correlation of radio measurements with a different, established method. At the moment, the Xmax resolution of Tunka-Rex is approximately 40 g/cm2. This resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations.

A comparison of the cosmic-ray energy scales of Tunka-133 and KASCADE-Grande via their radio extensions Tunka-Rex and LOPES

Abstract The radio technique is a promising method for detection of cosmic-ray air showers of energies around 100 PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately 10 % – limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level.

Revised absolute amplitude calibration of the LOPES experiment

Abstract One of the main aims of the LOPES experiment was the evaluation of the absolute amplitudeof the radio signal of air showers. This is of special interest since the radio technique offers the pos-sibility for an independent and highly precise determination of the energy scale of cosmic rays onthe basis of signal predictions from Monte Carlo simulations. For the calibration of the amplitudemeasured by LOPES we used an external source. Previous comparisons of LOPES measurementsand simulations of the radio signal amplitude predicted by CoREAS revealed a discrepancy of theorder of a factor of two. A re-measurement of the reference calibration source, now performed forthe free field, was recently performed by the manufacturer. The updated calibration values leadto a lowering of the reconstructed electric field measured by LOPES by a factor of 2:6 0:2 andtherefore to a significantly better agreement with CoREAS simulations. We discuss the updatedcalibration and its impact on the LOPES analysis results.2

Tunka-Rex: A radio antenna array for the Tunka experiment

Tunka-Rex, the Tunka radio extension, is an array of 20 antennas at the Tunka experiment close to Lake Baikal in Siberia. It started operation on 08 October 2012. The antennas are connected directly to the data acquisition of the Tunka main detector, a 1km2 large array of 133 non-imaging photomultipliers observing the Cherenkov light of air showers in dark and clear nights. This allows to cross-calibrate the radio signal with the air-Cherenkov signal of the same air showers - in particular with respect to the energy and the atmospheric depth of the shower maximum, Xmax. Consequently, we can test whether in rural regions with low radio background the practically achievable radio precision comes close to the precision of the established fluorescence and air-Cherenkov techniques. At a mid-term perspective, due to its higher duty-cycle, Tunka-Rex can enhance the effective observing time of Tunka by an order of magnitude, at least in the interesting energy range above 100PeV. Moreover, Tunka-Rex is very cost-e...

Towards a cosmic-ray mass-composition study at Tunka Radio Extension

The Tunka Radio Extension (Tunka-Rex) is a radio detector at the TAIGA facility located in Siberia nearby the southern tip of Lake Baikal. Tunka-Rex measures air-showers induced by high-energy cosmic rays, in particular, the lateral distribution of the radio pulses. The depth of the air-shower maximum, statistically depends on the mass of the primary particle, is determined from the slope of the lateral distribution function (LDF). Using a model-independent approach, we have studied possible features of the one-dimensional slope method and tried to find improvements for the reconstruction of primary mass. To study the systematic uncertainties given by different primary particles, we have performed simulations using the CONEX and CoREAS software packages of the recently released CORSIKA v7.5 including the modern high-energy hadronic models QGSJet-II.04 and EPOS-LHC. The simulations have shown that the largest systematic uncertainty in the energy deposit is due to the unknown primary particle. Finally, we studied the relation between the polarization and the asymmetry of the LDF.

The TAIGA experiment: from cosmic ray to gamma-ray astronomy in the Tunka valley

The physical motivations and advantages of the new gamma-observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is presented. The TAIGA array is a complex, hybrid detector for ground-based gamma-ray astronomy for energies from a few TeV to several PeV as well as for cosmic ray studies from 100 TeV to several EeV. The TAIGA will include the wide angle Cherenkov array TAIGA-HiSCORE with ~5 km2 area, a net of 16 I ACT telescopes (with FOV of about 10x10 degree), muon detectors with a total area of up to 2000-3000 m2 and the radio array Tunka-Rex.

Calibration of the absolute amplitude scale of the tunka radio extension (Tunka-Rex)

R. Hiller∗1, P.A. Bezyazeekov2, N.M. Budnev2, O.A. Gress2, A. Haungs1, T. Huege1, Y. Kazarina2, M. Kleifges3, E.N. Konstantinov2, E.E. Korosteleva4, D. Kostunin1, O. Kromer3, L.A. Kuzmichev4, N. Lubsandorzhiev4, R.R. Mirgazov2, R. Monkhoev2, A. Pakhorukov2, L. Pankov2, V.V. Prosin4, G.I. Rubtsov5, F.G. Schroder1, R. Wischnewski6, A. Zagorodnikov2 Tunka-Rex Collaboration 1 Institut fur Kernphysik, Karlsruhe Institute of Technology (KIT), Germany 2 Institute of Applied Physics ISU, Irkutsk, Russia 3 Institut fur Prozessdatenverarbeitung und Elektronik, Karlsruhe Inst. of Tech. (KIT), Germany 4 Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia 5 Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia 6 DESY, Zeuthen, Germany E-mail: roman.hiller@kit.edu

Status and first results of the Tunka Radio Extension

R. Hiller, N.M. Budnev, O.A. Gress, A. Haungs, T. Huege, Y. Kazarina, M. Kleifges, A. Konstantinov , E.N. Konstantinov , E.E. Korosteleva, D. Kostunin, O. Kromer, L.A. Kuzmichev, R.R. Mirgazov, L. Pankov, V.V. Prosin, G.I. Rubtsov, C. Ruhle, F.G. Schroder, E. Svetnitsky , R. Wischnewski, A. Zagorodnikov (Tunka-Rex Collaboration) Institut fur Kernphysik, Karlsruhe Institute of Technology (KIT), Germany Institute of Applied Physics ISU, Irkutsk, Russia Institut fur Prozessdatenverarbeitung und Elektronik, KIT, Germany Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia 5 Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia DESY, Zeuthen, Germany *E-Mail: roman.hiller@kit.edu

Tunka-Rex: a Radio Extension of the Tunka Experiment

Tunka-Rex, the Tunka radio extension, is an array of about 20 antennas currently under construction, which covers an area of 1 km2. Tunka-Rex measures the radio emission of cosmic-ray air showers above 1016 eV. It is triggered by the photomultipliers of the Tunka-133 experiment which simultaneously measure the Cherenkov light emitted by the same air showers. The radio-Cherenkov-hybrid measurements thus offer a unique opportunity for a cross-calibration of both detection methods. The main goal of Tunka-Rex is to determine the precision of the radio reconstruction for the energy and the atmospheric depth of the shower maximum, Xmax, and thus to experimentally test theoretical predictions that the radio precision can be similar to the precision of air-Cherenkov and fluorescence measurements. At the same time, Tunka-Rex can demonstrate that radio measurements can be performed on a large area for a relatively cheap price, since the antennas will be connected to the already existing Tunka DAQ. Finally, radio-antenna arrays have the perspective to increase the effective observation time compared to air-Cherenkov and fluorescence detectors by an order of magnitude, since radio measurements are possible under almost any atmospheric and light conditions.

Tunka-Rex: Status, Plans, and Recent Results

Tunka-Rex, the Tunka Radio extension at the TAIGA facility (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) in Siberia, has recently been expanded to a total number of 63 SALLA antennas, most of them distributed on an area of one square kilometer. In the first years of operation, Tunka-Rex was solely triggered by the co-located air-Cherenkov array Tunka-133. The correlation of the measurements by both detectors has provided direct experimental proof that radio arrays can measure the position of the shower maximum. The precision achieved so far is 40 g/cm2 , and several methodical improvements are under study. Moreover, the cross-comparison of Tunka-Rex and Tunka-133 shows that the energy reconstruction of Tunka-Rex is precise to 15 %, with a total accuracy of 20 % including the absolute energy scale. By using exactly the same calibration source for Tunka-Rex and LOPES, the energy scale of their host experiments, Tunka-133 and KASCADE-Grande, respectively, can be compared even more accurately with a remaining uncertainty of about 10 %. The main goal of Tunka-Rex for the next years is a study of the cosmic-ray mass composition in the energy range above 100 PeV: For this purpose, Tunka-Rex now is triggered also during daytime by the particle detector array Tunka-Grande featuring surface and underground scintillators for electron and muon detection.