We present the first Ge-based constraints on sub-MeV /c2 dark matter (DM) particles interacting with electrons using a 33.4 g Ge cryogenic detector with a 0.53 electron-hole pair (rms) resolution, ...operated underground at the Laboratoire Souterrain de Modane. Competitive constraints are set on the DM-electron scattering cross section, as well as on the kinetic mixing parameter of dark photons down to 1 eV / c2. In particular, the most stringent limits are set for dark photon DM in the 6 to 9 eV / c2 range. These results demonstrate the high relevance of Ge cryogenic detectors for the search of DM-induced eV-scale electron signals.
We make use of the EDELWEISS-III array of germanium bolometers to search for electron interactions at the keV scale induced by phenomena beyond the Standard Model. A 90% C.L. lower limit is set on ...the electron lifetime decaying to invisibles, ?>1.2×1024 years. We investigate the emission of axions or axionlike particles (ALPs) by the Sun, constraining the coupling parameters gae<1.1×10?11 and gae×gaNeff<3.5×10?17 at 90% C.L. in the massless limit. We also directly search for the absorption of bosonic dark matter particles that would constitute our local galactic halo. Limits are placed on the couplings of ALPs or hidden photon dark matter in the mass range 0.8–500 keV/c2. Prospects for searching for dark matter particles with masses down to 150 eV/c2 using improved detectors are presented.
We report on a dark matter search for a Weakly Interacting Massive Particle (WIMP) in the mass range
m
χ
∈
4
,
30
GeV
/
c
2
with the EDELWEISS-III experiment. A 2D profile likelihood analysis is ...performed on data from eight selected detectors with the lowest energy thresholds leading to a combined fiducial exposure of 496 kg-days. External backgrounds from
γ
- and
β
-radiation, recoils from
206
Pb
and neutrons as well as detector intrinsic backgrounds were modelled from data outside the region of interest and constrained in the analysis. The basic data selection and most of the background models are the same as those used in a previously published analysis based on boosted decision trees (BDT)
1
. For the likelihood approach applied in the analysis presented here, a larger signal efficiency and a subtraction of the expected background lead to a higher sensitivity, especially for the lowest WIMP masses probed. No statistically significant signal was found and upper limits on the spin-independent WIMP-nucleon scattering cross section can be set with a hypothesis test based on the profile likelihood test statistics. The 90 % C.L. exclusion limit set for WIMPs with
m
χ
=
4
GeV
/
c
2
is
1.6
×
10
-
39
cm
2
, which is an improvement of a factor of seven with respect to the BDT-based analysis. For WIMP masses above
15
GeV
/
c
2
the exclusion limits found with both analyses are in good agreement.
We present an improved method for the precise reconstruction of cosmic-ray air showers above 1017 eV with sparse radio arrays. The method is based on the comparison of measured pulses to predictions ...for radio pulse shapes by CoREAS simulations. We applied our method to the data of Tunka-Rex, a 1 km2 radio array in Siberia operating in the frequency band of 30–80 MHz. Tunka-Rex is triggered by the air-Cherenkov detector Tunka-133 and by scintillators (Tunka-Grande). The instrument collects air-shower data since 2012. The present paper describes an updated data analysis of Tunka-Rex and details of the new method applied. After quality cuts, when Tunka-Rex reaches its full efficiency, the energy resolution of about 10% given by the new method has reached the limit of systematic uncertainties due to the calibration uncertainty and shower-to-shower fluctuations. At the same time the shower maximum reconstruction has improved compared to the previous method based on the slope of the lateral distribution and reaches a precision of better than 35 g/cm2. We also define conditions of the measurements at which the shower maximum resolution of Tunka-Rex reaches a value of 25 g/cm2 and becomes competitive to optical detectors. To check and validate our reconstruction and efficiency cuts we compare individual events to the reconstruction of Tunka-133. Furthermore, we compare the mean of the shower maximum as a function of primary energy to the measurements of other experiments.
The Pierre Auger Observatory is the largest installation worldwide for the investigation of ultra-high energy cosmic rays. Air showers are detected using a hybrid technique with 27 fluorescence ...telescopes and 1660 water-Cherenkov detectors (WCD) distributed over about 3000km2. The Auger Collaboration has decided to upgrade the electronics of the WCD and complement the surface detector with scintillators (SSD). The objective is to improve the separation between the muonic and the electron/photon shower component for better mass composition determination during an extended operation period of 8–10years. The surface detector electronics records data locally and generates time stamps based on the GPS timing. The performance of the detectors is significantly improved with a higher sampling rate, an increased dynamic range, new generation of GPS receivers, and FPGA integrated CPU power. The number of analog channels will be increased to integrate the new SSD, but the power consumption needs to stay below 10W to be able to use the existing photovoltaic system. In this paper, the concept of the additional SSD is presented with a focus on the design and performance of the new surface detector electronics.
The Pierre Auger Observatory is a hybrid experiment to observe cosmic ray extensive air showers with energies above
10
19
eV
by a combination of a surface array and air fluorescence detectors (FD). ...Prototypes of both these detectors have been successfully tested and operated. Currently the final design version of the electronics is undergoing installation. Based on experience gained with the prototype we present the concept of the FD electronics and the implemented trigger algorithms. The electronics continuously record the image of the 20×22 pixel camera in a ring buffer of
100
μs
length with a time resolution of
100
ns
. Digital trigger algorithms analyse these data to find straight tracks originating from the fluorescence light. All individual detectors are synchronized with a
10
MHz
signal generated by a GPS clock module. Veto and dead time signals are centrally distributed to allow calibration with external light sources during normal operation. A statistical method for the calibration was developed and tested.
A measurement of the absolute fluorescence yield of the 337 nm nitrogen band, relevant to ultra-high energy cosmic ray (UHECR) detectors, is reported. Two independent calibrations of the fluorescence ...emission induced by a 120 GeV proton beam were employed: Cherenkov light from the beam particle and calibrated light from a nitrogen laser. The fluorescence yield in air at a pressure of 1013 hPa and temperature of 293 K was found to be Y 337 = 5.61 +/- 0.06 stat +/- 0.22 syst photons/MeV. When compared to the fluorescence yield currently used by UHECR experiments, this measurement improves the uncertainty by a factor of three, and has a significant impact on the determination of the energy scale of the cosmic ray spectrum.
The Pierre Auger Observatory studies cosmic ray extensive air showers with energies at and above the EeV range with a hybrid instrument consisting of a surface detector array and air fluorescence ...telescopes. Science results obtained with the southern observatory located near Malargüe, Province of Mendoza, Argentina, are the driving force to build a second observatory in southeast Colorado (USA) in the rural environment of Lamar. This Auger North Observatory will focus on measurements in the highest energy range above 50 EeV with the highest possible acceptance. As a consequence of the different energy range of the southern and northern sites, the designs of the instruments are different in some aspects. We present the proposed Auger North layout, the changes in the design of the detectors, and the current site activities with the Research and Development Array (RDA).
The Tunka Radio Extension (Tunka-Rex) is an antenna array spread over an area of about 1 km2. The array is placed at the Tunka Advanced Instrument for cosmic rays and Gamma Astronomy (TAIGA) and ...detects the radio emission of air showers in the band of 30 to 80 MHz. During the last years it was shown that a sparse array such as Tunka-Rex is capable of reconstructing the parameters of the primary particle as accurate as the modern instruments. Based on these results we continue developing our data analysis. Our next goal is the reconstruction of cosmic-ray energy spectrum observed only by a radio instrument. Taking a step towards it, we develop a model of aperture of our instrument and test it against hybrid TAIGA observations and Monte-Carlo simulations. In the present work we give an overview of the current status and results for the last five years of operation of Tunka-Rex and discuss prospects of the cosmic-ray energy estimation with sparse radio arrays.
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