A STUDY OF THE TRANSVERSE FLUCTUATIONS OF HADRONIC SHOWERS IN THE NOMAD ELECTROMAGNETIC CALORIMETER

The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and inciden t angles. Large event-to-event fluctuations in the shower shape and si gnificant energy depositions far from the incident hadron were observe d making it difficult to associate all the deposited energy to the inc ident hadron that caused it. Since in the NOMAD detector the momenta o f charged hadrons are measured by a magnetic spectrometer, such an ass ociation is necessary to be able to subtract from the calorimeter ail the energy caused by the observed charged hadrons in order to avoid do uble counting. Probability functions based on the measurements have be en developed to describe fluctuations of the lateral shower shape. Sta rting from these Functions, an algorithm is developed for identifying the energy deposition associated to a charged hadron. The identificati on and separation of overlapping showers based on these functions is a lso discussed. The Monte Carlo simulation of the calorimeter reproduce s the test beam data well therefore allowing the application of the al gorithm at angles and momenta not studied in the test beam. (C) 1998 E lsevier Science B.V. All rights reserved.