BEXCO - Room A(101/102)
[CRI209] Depth of maximum of air-shower profiles at the Pierre Auger Observatory: Measurements and composition
We present shower depth of maximum (Xmax) distributions and their interpretation in terms of the cosmic ray mass composition. The measurements of Xmax are based on data from the fluorescence telescopes of the Pierre Auger Observatory. Due to the extension of the field of view with the High Elevation Auger Telescopes, a lower energy threshold of 10^17.2 eV can be reached. At the highest energies we have increased the available statistics by including three years more data in the analysis compared to our previous publications. We present estimates of the first two moments of the Xmax distribution and of the composition fractions over a large energy range, from 10^17.2 to above 10^19.6 eV. The composition fractions are estimated by fitting the Xmax distributions with four elemental groups represented by p, He, N and Fe.