Effect on a Hadron Shower Leakage on the Energy Response and Resolution of Hadron TILE Calorimeter

The hadronic shower longitudinal and lateral leakages and its effect on the pion response and energy resolution of ATLAS ironscintillator barrel hadron prototype calorimeter with longitudinal tile configuration with a thickness of 9.4 nuclear interaction lengths have been investigated. The results are based on 100 GeV pion beam data at incidence angle Θ = 10 at impact point Z in the range from −36 to 20 cm which were obtained during test beam period in May 1995 with setup equipped scintillator detector planes placed behind and back of the calorimeter. The fraction of the energy of 100 GeV pions at Θ = 10 leaking out at the back of this calorimeter amounts to 1.8% and agrees with the one for a conventional iron-scintillator calorimeter. Unexpected behaviour of the energy resolution as a function of leakage is observed: 6% lateral leakage lead to 18% improving of energy resolution in compare with the showers without leakage. The measured values of longitudinal punchthrough probability (18 ± 1)% and (20 ± 1)% for two different hit definitions of leaking events agree with the earlier measurement for our calorimeter and with the one for a conventional iron-scintillator calorimeter with the same nuclear interaction length thickness respectively. Due to more soft cut for hit definition in the leakage detectors the measured value of longitudinal punchthrough probability more corresponds to the calculated iron equivalent length LFe = 158 cm.