Reconstruction of the primary energy of UHE photon-induced showers from Auger SD

GERMÁN ROS; G MEDINA-TANCO; A.D. SUPANITSKY; LUIS DEL PERAL; MAR ́ıA DOLORES RODRÍGUEZ-FRÍAS

Malargüe

Otro; Reunion de la Colaboración Internacional Pierre Auger; 2010

Colaboración Internacional Pierre Auger

In this GAP we review the procedure to determine the energy of the photon-initiated showers as it has been used in the Auger paper about the photon limit with the surface detector [1]. This method is based on the paper by P. Billoir et al. [2]. The technique relies on the universality of the photon showers, which are almost purely electromagnetic, and consists of an iterative process where the energy and X_max are alternatively determined using Monte Carlo parametrizations. Themethod works properly but the parameters initially proposed in [2] must be modified if S(1000), which is needed in the iterative process, is obtained from the standard SD reconstruction algorithm implemented in Offline [3,4]. In addition, we show that, while this method achieves good energy resolution (around 18%) without bias, it is not adequate to infer X max of photon showers indirectly from SD.