  We examine here the acceleration of particles and high energy collisions in
the the Janis-Newman- Winicour (JNW) spacetime, which is an extension of the
Schwarzschild geometry when a massless scalar field is included. We show that
while the center of mass energy of collisions of particles near the event
horizon of a blackhole is not significantly larger than the rest mass of the
interacting particles, in an analogous situation, it could be arbitrarily large
in the JNWspacetime near the naked singularity. The high energy collisions are
seen to be generic in the presence of a photon sphere in the JNW spacetime,
whereas an extreme fine-tuning of the angular momentum of the colliding
particles is required when the photon sphere is absent. The center of mass
energy of collision near the singularity grows slowly for small and extremely
large deviations from the Schwarzschild blackhole, but for intermediate
strengths of the scalar field it rises moderately fast. As a possible and
potentially interesting application, we point out that the presence of such
high energy collissions may help the blackhole configurations to be
distinguished from a naked singularity.
