The impact of the air-fluorescence yield on the reconstructed shower parameters of ultra-high energy cosmic rays

Abstract

An accurate knowledge of the fluorescence yield and its dependence on atmospheric properties such as pressure, temperature or humidity is essential to obtain a reliable measurement of the primary energy of cosmic rays in experiments using the fluorescence technique. In this work, several sets of fluorescence yield data (i.e. absolute value and quenching parameters) are described and compared. A simple procedure to study the effect of the assumed fluorescence yield on the reconstructed shower parameters (energy and shower maximum depth) as a function of the primary features has been developed. As an application, the effect of water vapor and temperature dependence of the collisional cross section on the fluorescence yield and its impact on the reconstruction of primary energy and shower maximum depth has been studied.

The effect of the fluorescence yield selection on the energy scales of Auger, HiRes and TA

“…The corresponding ∆E values for a typical vertical shower at 15km from the telescope are also shown in the table (columns 3 and 4). These calculations have been repeated including the temperature and humidity contributions to the P λ values in Auger with typical atmospheric profiles (see [2] for details). As shown in the table (columns 5 and 6), the disagreement between the relative energy scales for both cases HiRes-Auger and TA-Auger is partly cancelled.…”

“…Note that even if the assumed true yield turns out to be wrong by a scale factor, expressions (4) and (5) are still valid, that is Y t only needs to describe the true relative fluorescence spectrum. The above procedure allows the evaluation of the deviation in the energy deposition at a given atmospheric depth due to a change in the fluorescence yield (2) or in both fluorescence yield and optical efficiency (4,5). The corresponding effect on the total calorimetric energy of the shower can also be calculated from the above expressions as long as we replace the above dentition, Yε ≡ λ Y λ ε λ , by the following one…”

“…Using (6) has allowed us to calculate more realistically the energy deviations. For the development of deposited energy, a Gaisser-Hillas profile has been used and the T λ values have been computed from [11] (see [2] for details).…”

“…Neglecting the humidity contribution to quenching and the temperature dependence of the collisional cross section, the differences in the assumed P λ values do not lead to significant disagreements in the energy reconstruction, since most of the shower energy is deposited in the lower atmospheric layers where quenching effects saturate. However these humidity and temperature contributions to P λ give rise to a non-negligible effect on the reconstructed energy [2].…”

Nitrogen fluorescence in air for observing extensive air showers

“…These groups have been discussing their techniques and data in a series of Air Fluorescence Workshops (AFW) commenced in Utah, 2002 [9]. Main results are contributed by the following alphabetic list of collaborations and groups led by their principal investigators: AIRFLY [10,11,12,13,14,15], Airlight [16,17], Arqueros/UCM [18,19,20,21,22], FLASH [23,24,25,26], Fraga/LIP [27,28], Keilhauer/KIT [29,30,31], Lefeuvre/APC [32], MACFLY [33], Nagano/Sakaki [34,35,36], and Ulrich/TUM [37,38,39,40]. At the up to now last Air Fluorescence Workshop in Karlsruhe, 2011, it was decided to develop a common fluorescence description for application at air shower reconstructions [9].…”