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Photon air showers at ultra-high energy and the photonuclear cross-section

M. Risse·P. Homola·R. Engel·D. Gora·D. Heck·J. Pekala·B. Wilczynska·H. Wilczynski
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Abstract

Experimental conclusions from air shower observations on cosmic-ray photons above 10^19 eV are based on the comparison to detailed shower simulations. For the calculations, the photonuclear cross-section needs to be extrapolated over several orders of magnitude in energy. The uncertainty from the cross-section extrapolation translates into an uncertainty of the predicted shower features for primary photons and, thus, into uncertainties for a possible data interpretation. After briefly reviewing the current status of ultra-high energy photon studies, the impact of the uncertainty of the photonuclear cross-section for shower calculations is investigated. Estimates for the uncertainties in the main shower observables are provided. Photon discrimination is shown to be possible even for rapidly rising cross-sections. When photon-initiated showers are identified, it is argued that the sensitivity of photon shower observables to the photonuclear cross-section can in turn be exploited to constrain the cross-section at energies not accessible at colliders.

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M. Risse, P. Homola, R. Engel, D. Gora, D. Heck, J. Pekala, B. Wilczynska, H. Wilczynski. 2005-12-16. Photon air showers at ultra-high energy and the photonuclear cross-section. https://doi.org/10.1007/s10582-006-0166-7

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