  In addition to the gamma-ray binaries which contain a compact object, high
energy (HE) and very high energy (VHE) gamma-rays have also been detected from
colliding-wind binaries. The collision of the winds produces two strong shock
fronts, one for each wind, both surrounding a shock region of compressed and
heated plasma, where particles are accelerated to very high energies. Magnetic
field is also amplified in the shocked region, on which the acceleration of
particles greatly depends. In this work we performed full three-dimensional
magnetohydrodynamic simulations of colliding winds, coupled to a code that
evolves the kinematics of passive charged test particles subject to the plasma
fluctuations. After the run of a large ensemble of test particles with initial
thermal distributions we show that such shocks produce a non-thermal population
(nearly 1% of total particles) of few tens of GeVs up to few TeVs, depending on
the initial magnetization level of the stellar winds. We were able to determine
the loci of fastest acceleration, in the range of MeV/s to GeV/s, to be related
to the turbulent plasma with amplified magnetic field of the shock. These
results show that colliding wind binaries are indeed able to produce a
significant population of high energy particles, in relatively short
timescales, compared to the dynamical and diffusion timescales.
