The course of non-thermal electron ejection in relativistic unmagnetized electron-ion shocks is investigated by performing self-consistent particle-in-cell simulations .
The shocks are excited through the injection of relativistic jet into ambient plasma , leading to two distinct shocks ( named as the trailing shock and leading shock ) and a contact discontinuity .
The Weibel-like instabilities heat the electrons up to approximately half of ion kinetic energy .
The double layers formed in the trailing and leading edges then accelerated the electrons by the ion kinetic energy .
The electron distribution function in the leading edge shows a clear non-thermal power-law tail which contains \sim 1 \% of electrons and \sim 8 \% of electron energy .
Its power-law index is -2.6 .
The acceleration efficiency is \sim 23 \% by number and \sim 50 \% by energy and the power-law index is -1.8 for electron distribution function in the trailing edge .
The effect of the dimensionality is examined by comparing results of 3D simulation with 2D ones .
It exhibits that the electron acceleration is more efficient in 2D .