Average value of available measurements of the air-fluorescence yield

摘要

The air-fluorescence yield is a key parameter for determining the energy scale of ultra-high-energy cosmic raysdetected by fluorescence telescopes. For comparison purposes, available measurements of the absolute air-fluorescenceyield have been normalized to common units and same experimental conditions. Corrections in the evaluation of energydeposition are proposed for some experiments. A simple statistical analysis shows that these corrections favor thecompatibility among the various experiments. As a result, an average value of 5.45 ph/MeV for the fluorescence yieldof the 337 nm band (20.1 ph/MeV for the spectral interval 300 - 420 nm) at 1013 hPa and 293 K with an uncertaintyof around 5% is found. This result is fully compatible with that recently presented by the AIRFLY collaboration (stillpreliminary) in such a way that including this latest result could even lowered the final uncertainty below the 5% levelwith high reliability.