TY  - THES
AB  - An analysis of the mass composition of UHECRs based on the Xmax elongation 
rate (ER) within the energy range 10^{17.8} -10^{20.0} eV is performed, using  Xmax data collected by the Pierre Auger Observatory from December  2004 to December 2012. The development of ER with energy is investigated  by 
estimating the ER and the rate of change of ER with energy in sliding windows.
In order to make it easier to observe the effect of a change in the proton fraction on the overall primary cosmic ray composition, the data has been truncated into "light" and "heavy" components based on a cut on the Xmax value above which 50% of helium showers produced with EPOS-LHC survive. The "light" component should be dominated by proton and helium nuclei. The behavior of the ER of the "light" part  potentially allows one to distinguish  changes in the mass composition from  changes in the properties of hadronic interactions.
     The rate of change of ER with energy is observed to be negative and differs from zero for lg(E/eV) approx 18.2-18.5 by approx 3 sigma: primary mass is increasing and the rate of change of primary mass might not be constant. The increase in primary mass  might be mostly due to a reduction of the fraction of protons. The "heavy" subset seems to be consistent with a constant primary mass. An  interpretation of the data as being due to a pure proton composition with an unexpectedly large increase in interaction cross-section might be in tension with the behavior of ER of the "light" component.
AU  - Ochilo, Livingstone
DA  - 2016
KW  - Pierre-Auger-Observatorium
KW  - Massenzusammensetzung
KW  - Elongationsrate
KW  - elongation rate
KW  - shower maximum
KW  - mass composition
LA  - eng
PY  - 2016
TI  - Mass composition of ultra-high energy cosmic rays : a study based on elongation rate of depth of shower maximum measured at the Pierre Auger Observatory
UR  - https://nbn-resolving.org/urn:nbn:de:hbz:467-10184
Y2  - 2024-12-26T21:30:05
ER  -