Lifetimes of the Heavy Neutral Leptons in the Okamura Model
  We study the lifetimes of TeV-scale heavy neutral leptons (Majorana neutrinos) that appear in a model suggested by Okamura et al. [2]. We develop a convenient way to parametrize the neutrino mass texture of the model, and illustrate our method by calculating the mass spectrum, decay widths, and lifetimes of the heavy particles over the entire parameter space. From the mass spectrum, we find that for most of the parameter space, only two-body decays are relevant in the calculation of the lifetime, with typical values falling in the range of 10^(-26) to 10^(-24) seconds. If the particles discussed here are created at colliders, their lifetimes are short enough for them to decay inside the detector, while long enough to lead to a narrow peak in the invariant mass spectrum of the decay products. However, an analysis by Dicus, Karatas, and Roy [16] suggests that they may be difficult to observe at the LHC. 
Alexey Pronin, Tatsu Takeuchi