Related papers: UHECR Composition Measurements Using the HiRes-II …
We report an investigation of the mass composition of cosmic rays with energies from 3 to 100 EeV (1 EeV=$10^{18}$ eV) using the distributions of the depth of shower maximum $X_\mathrm{max}$. The analysis relies on ${\sim}50,000$ events…
This paper presents the highlights from the recent measurements of the energy spectrum, mass composition, and arrival directions of the ultra-high energy ($> 10^{17}$ eV = 0.1 EeV) cosmic rays (UHECR) by the Pierre Auger Observatory. The…
Using the data taken at the Pierre Auger Observatory between December 2004 and December 2012, we have examined the implications of the distributions of depths of atmospheric shower maximum (Xmax), using a hybrid technique, for composition…
We have measured the spectrum of UHE cosmic rays using the Flash ADC (FADC) detector (called HiRes-II) of the High Resolution Fly's Eye experiment running in monocular mode. We describe in detail the data analysis, development of the Monte…
The simple interpretation of PAO's UHECRs' penetration depth measurements suggests a transition at the energy range $1.1 - 35 \cdot 10^{18} $ eV from protons to heavier nuclei. A detailed comparison of this data with air shower simulations…
In this paper Ultra High Energy Cosmic Rays UHECRs data observed by the HiRes fluorescence detector in stereo mode is analyzed to search for events in the sky with an arrival direction lying on a great circle. Such structure is known as the…
Measurements are reported on the fluorescence of air as a function of depth in electromagnetic showers initiated by bunches of 28.5 GeV electrons. The light yield is compared with the expected and observed depth profiles of ionization in…
We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above $5 \cdot 10^{18}$ eV,…
More than two years of fluorescence detector data collected in coincidence with at least one station of the surface detector array (``hybrid data'') are used to measure the flux and energy spectrum of cosmic rays above about 10$^{18}$ eV.…
The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10^20 eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within ~50 Mpc through interactions with the cosmic microwave background. As…
Measuring the angles of muons and electrons in air showers is proposed as a method for studying the primary cosmic-ray mass composition near the knee of the cosmic-ray energy spectrum at a few $10^{15}$ eV. Conventional tracking detectors…
The fluorescence technique has been successfully used to detect ultrahigh energy cosmic rays by indirect measurements. The underlying idea is that the number of charged particles in the atmospheric shower, i.e, its longitudinal profile, can…
We present a new methodology to discriminate between light and heavy ultra-high energy cosmic-ray primaries on an event-by-event basis using information from the radio detection of extensive air showers at MHz frequencies. Similarly to…
We present a summary of the measurements of mass sensitive parameters at the highest cosmic ray energies done by several experiments. The Xmax distribution as a function of energy has been measured with fluorescence telescopes by the HiRes,…
We propose a new method for the estimation of ultra-high energy cosmic ray (UHECR) mass composition from a distribution of their arrival directions. The method employs a test statistic (TS) based on a characteristic deflection of UHECR…
Modern observatories of ultra-high energy cosmic rays (UHECR) have collected over 10^4 events with energies above 10 EeV, whose arrival directions appear to be nearly isotropically distributed. On the other hand, the distribution of matter…
The determination of the mass composition of the highest energy cosmic rays is one of the greatest challenges in cosmic ray experiments. The highest energy cosmic rays are only detected indirectly because of their very low flux. Using the…
At higher energies the uncertainty in the estimated cosmic ray mass composition, extracted from the observed distributions of the depth of shower maximum $X_\text{max}$, is dominated by uncertainties in the hadronic interaction models.…
The current methods to determine the primary energy of ultra-high energy cosmic rays (UHECRs) are different when dealing with hadron or photon primaries. The current experiments combine two different techniques, an array of surface…
We report on studies of the composition of ultra high energy cosmic rays with the Pierre Auger Observatory. The detection of longitudinal air shower profiles with the fluorescence detector is described and the measurement of the average…