Measurements and tests of hadronic interactions at ultra-high energies with the Pierre Auger Observatory

Abstract

Extensive air showers are complex objects, resulting of billions of particle reactions initiated by single cosmic ray at ultra-high-energy. Their characteristics are sensitive both to the mass of the primary cosmic ray and to the details of hadronic interactions. Many of the interactions that determine the shower features occur in kinematic regions and at energies beyond those tested by human-made accelerators. We will report on the measurement of the proton-air cross section for particle production at a center-of-mass energy per nucleon of 39 TeV and 56 TeV. We will also show comparisons of post-LHC hadronic interaction models with shower data by studying the moments of the distribution of the depth of the electromagnetic maximum, the number and production depth of muons in air showers, and finally a parameter based on the risetime of the surface detector signal, sensitive to the electromagnetic and muonic component of the shower. While there is good agreement found for observables based on the electromagnetic shower component, discrepancies are observed for muon-sensitive quantities. *

Probing hadronic interactions with measurements from the Pierre Auger Observatory

“…Predictions for proton and iron primaries for two hadronic interaction models are also shown. [6] with the SD, produce systematically smaller signals in the simulations than the ones found in the data. For each event, batches of simulations were generated using the measured energy and geometry as inputs and considering different primaries.…”

Particle Physics with the Pierre Auger Observatory

“…Figure 2: Left: The energy evolution of the average muon content R µ measured by AMIGA (white circles) and by the SD using horizontal air showers (black circles) [8]. Right: Average logarithmic muon content as a function of the average shower depth X max [7].…”

Probing hadronic interactions with measurements from the Pierre Auger Observatory

“…Predictions for proton and iron primaries for two hadronic interaction models are also shown. [6] The measured signals in the WCDs derive from both muons and electromagnetic particles and these contributions cannot be easily decoupled. However, it is straightforward to obtain both the electromagnetic and hadronic parts of the signal when using simulations.…”