Analysis of neutrino interactions and search for neutral heavy particles with the front calorimeter of the NOMAD experiment

The NOMAD detector at CERN was designed for the appearance search of tau neutrinos in the CERN wide-band neutrino beam, predominantly composed of muon type neutrinos. Neutrino interactions in the front calorimeter (FCAL) of the detector accumulated during the 1996-1998 data taking periods have been analyzed. A search for muon type neutral heavy leptons (NHL) produced by neutral-current muon neutrino interactions in the FCAL target and decaying into final states including a muon has been conducted. No evidence for the existence of such a particle has been found. The results have been parametrized in terms of a Grand Unification Theory (GUT) NHL predicted to behave as a singlet under weak-isospin group of the Standard Model of particle physics.