Results on ββ decay with emission of two neutrinos or Majorons in 76Ge from GERDA Phase I

A search for neutrinoless beta beta decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices n = 1, 2, 3, 7 were searched for. No signals were found and lower limits of the order of 10(23) yr on their half-liveswere derived, yielding substantially improved results compared to previous experiments with Ge-76. A new result for the half-life of the neutrino-accompanied beta beta decay of Ge-76 with significantly reduced uncertainties is also given, resulting in T-1/1(2 nu) = (1.926 +/- 0.094) x 10(21) yr.