  Origin of ultra high energy cosmic rays is an unsolved problem. Several
proposals such as Z-burst, decay of super massive matter, susy particles as a
primary, neutrino as a primary in extra dimension models exist in the
literature which try to address this issue. Many of these proposals solve the
problem of propagation of cosmic rays over cosmological distances by
introducing new physics. However these do not explain the origin of such high
energy cosmic rays. The possible astrophysics sites, such as active galactic
nuclei, are highly constrained. Here we determine whether these cosmic rays
originated from the decay of some exotic objects, such as primordial black
holes (PBHs), present in the early universe. In contrast to the usual Top Down
scenario we do not assume that this exotic object necessarily has to decay in
our astrophysical neighbourhood since we assume a beyond the standard model
scenario, where the propagation problem is absent. We consider the standard
4-dimension PBHs as well as the brane world PBHs. We find that in both cases it
is unable to produce the observed ultra high energy cosmic ray flux.
