Hadronic Multiparticle Production at Ultra-High Energies and Extensive Air Showers

TL;DR

The article tackles the core problem of interpreting ultra-high-energy cosmic ray air showers under large uncertainties in hadronic multiparticle production beyond collider reach. It introduces an ad hoc modification framework that reshapes outputs of existing interaction models within EAS simulations, enabling systematic exploration of cross-section, multiplicity, elasticity, and pion-charge effects on observables like the depth of shower maximum ($X_{ m max}$) and ground-level muon/electron counts. By comparing results to the Heitler–Matthews cascade picture, the work shows that $X_{ m max}$ is most sensitive to cross-section extrapolations, while muon numbers are harder to tune and highly model-dependent; the invisible energy changes only modestly. The findings suggest that advancing forward-physics measurements at the LHC and integrating external composition information are essential to reducing uncertainties in cosmic ray interpretation at ultra-high energies.

Abstract

Studies of the nature of cosmic ray particles at the highest energies are based on the measurement of extensive air showers. Most cosmic ray properties can therefore only be obtained from the interpretation of air shower data and are thus depending on predictions of hadronic interaction models at ultra-high energies. We discuss different scenarios of model extrapolations from accelerator data to air shower energies and investigate their impact on the corresponding air shower predictions. To explore the effect of different extrapolations by hadronic interaction models we developed an ad hoc model. This ad hoc model is based on the modification of the output of standard hadronic interaction event generators within the air shower simulation process and allows us to study the impact of changing interaction features on the air shower development. In a systematic study we demonstrate the resulting changes of important air shower observables and also discuss them in terms of the predictions of the Heitler model of air shower cascades. It is found that the results of our ad hoc modifications are, to a large extend, independent of the choice of the underlying hadronic interaction model.

Figures (18)

• Figure 1: Compilation of accelerator data of $\sigma^{\rm pp}_{\rm tot}$ and $B_{\rm el}$Engel:2000pb. The central line denotes the conventional extrapolation of these data to high energy. The upper and lower lines indicate a set of possible extreme extrapolations. In the left plot the conventional model is the soft pomeron parametrization by Donnachie and Landshoff Donnachie:1992ny, while the lower curve is by Pancheri et al. Pancheri:2007rv and the upper one is the two-pomeron model of Landshoff Landshoff:2007ukLandshoff:2009wt. The different scenarios in the right plot are from Ulrich:2009yq.
• Figure 2: Uncertainty of the extrapolation of the proton-air cross section for particle production due to different models of the proton-proton cross section as calculated with the Glauber framework Ulrich:2009yq.
• Figure 3: Electromagnetic Heitler model.
• Figure 4: Hadronic Heitler-Matthews model: pion cascade in air.
• Figure 5: Fluctuation of the longitudinal air shower development for 20 proton induced EAS at $E_0=\unit[10^{19.5}]{eV}$.