Iskanje po repozitoriju

A+ | A- | | SLO | ENG

Opis: The Pierre Auger Observatory (Auger) in Mendoza, Argentina and the Telescope Array (TA) in Utah, USA aim at unraveling the origin and nature of Ultra-High Energy Cosmic Rays (UHECR). At present, there appear to be subtle differences between Auger and TA results and interpretations. Joint working groups have been established and have already reported preliminary findings. From an experimental standpoint, the Surface Detectors (SD) of both experiments make use of different detection processes not equally sensitive to the components of the extensive air showers making it to the ground. In particular, the muonic component of the shower measured at ground level can be traced back to the primary composition, which is critical for understanding the origin of UHECRs. In order to make direct comparisons between the SD detection techniques used by Auger and TA, a joint SD experimental research program is being developed. In the first phase, two Auger SD stations were deployed at the TA Central Laser Facility to compare station-level responses. This paper concentrates on the results obtained with the first Auger SD station (an “Auger North” design), which has been operating since October 2014. The second Auger SD station, identical to the ones being operated at Auger in Argentina (an “Auger South” design), was just deployed in June 2015. The second phase of this research program will be to co-locate six Auger North SD stations with TA stations in the field to compare event-level responses.
Ključne besede: Ultra-High Energy Cosmic Rays, Pierre Auger Observatory, Telescope Array, extensive air showers, secondary cosmic rays, muonic shower component, surface detectors
Objavljeno v RUNG: 08.03.2016; Ogledov: 6005; Prenosov: 191
Celotno besedilo (1,42 MB)

Opis: The Auger Engineering Radio Array (AERA) is an extension of the Pierre Auger Observatory. It is used to detect radio emission from extensive air showers in the 30 - 80 MHz frequency band. A focus of interest is the dependence of the radio emission on shower parameters such as the energy and the atmospheric depth of the shower maximum. After three phases of deployment, AERA now consists of 153 autonomous radio stations with different spacings, covering an area of about 17 km2. The size, station spacings, and geographic location at the same site or near other Auger extensions, are all targeted at cosmic ray energies above 10[sup]17 eV. The array allows us to explore different technical schemes to measure the radio emission as well as to cross calibrate our measurements with the established baseline detectors of the Auger Observatory. We present the most recent technological developments and selected experimental results obtained with AERA.
Ključne besede: Pierre Auger Observatory, the Auger Engineering Radio Array (AERA), radio emission from extensive air showers, detector cross-calibration
Objavljeno v RUNG: 03.03.2016; Ogledov: 6333; Prenosov: 202
Celotno besedilo (2,79 MB)

Opis: The Fluorescence Detector (FD) at the Pierre Auger Observatory measures the intensity of the scattered light from laser tracks generated by the Central Laser Facility (CLF) and the eXtreme Laser Facility (XLF) to monitor and estimate the vertical aerosol optical depth (τ(z,t)). This measurement is needed to obtain unbiased and reliable FD measurements of the arrival direction and energy of the primary cosmic ray, and the depth of the maximum shower development. The CLF was upgraded substantially in 2013 with the addition of a solid state laser, new generation GPS, a robotic beam calibration system, better thermal and dust isolation, and improved software. The upgrade also included a back-scatter Raman LIDAR to measure τ(z,t). The new features and applications of the upgraded instrument are described. These include the laser energy calibration and the atmospheric monitoring measurements. The first τ(z,t) results and comparisons after the upgrade are presented using different methods. The first method compares the FD hourly response to the scattered light from the CLF (or XLF) against a reference hourly profile measured during a clear night where zero aerosol contents are assumed. The second method simulates FD responses with different atmospheric parameters and selects the parameters that provide the best fit to the actual FD response. A third method uses the new Raman LIDAR receiver in-situ to measure the back-scatter light from the CLF laser. The results show a good data agreement for the first and second methods using FD stations located at the same distance from the facilities. Preliminary results of τ(z,t) using the Raman LIDAR are presented as well.
Ključne besede: Pierre Auger Observatory, extensive air showers, the Fluorescence Detector, atmospheric monitoring, vertical aerosol optical depth, the Central Laser Facility, the eXtreme Laser Facility
Objavljeno v RUNG: 03.03.2016; Ogledov: 6453; Prenosov: 184
Celotno besedilo (3,96 MB)

Opis: With hybrid data of the Pierre Auger Observatory it is possible to measure the cross section of proton-air collisions at energies far beyond the reach of the LHC. Since the first measurement by the Pierre Auger Collaboration the event statistics has increased significantly. The proton-air cross section is now estimated in the two energy intervals in lg(E/eV) from 17.8 to 18 and from 18 to 18.5. These energies are chosen so that they maximise the available event statistics and at the same time lie in the region most compatible with a significant primary proton fraction. Of these data, only the 20% of most proton-like events are considered for the measurement. Furthermore, with a new generation of hadronic interaction models which have been tuned to LHC data, the model-dependent uncertainties of the measurement are re-visited.
Ključne besede: Pierre Auger Observatory, extensive air showers, proton-air cross section, hadronic interaction models
Objavljeno v RUNG: 03.03.2016; Ogledov: 5801; Prenosov: 199
Celotno besedilo (114,02 KB)

Opis: Ultra-relativistic magnetic monopoles, possibly a relic of phase transitions in the early universe, would deposit an amount of energy comparable to UHECRs in their passage through the atmosphere, producing highly distinctive air shower profiles. We have performed a search for ultra-relativistic magnetic monopoles in the sample of air showers with profiles measured by the fluorescence detector of the Pierre Auger Observatory. No candidate was found to satisfy our selection criteria and we establish upper limits on the flux of ultra-relativistic magnetic monopoles - the first from an UHECR detector - improving over previous results by up to an order of magnitude.
Ključne besede: ultra-relativistic magnetic monopoles, extensive air showers, Pierre Auger Observatory
Objavljeno v RUNG: 03.03.2016; Ogledov: 5967; Prenosov: 199
Celotno besedilo (188,24 KB)