Charged dilation black holes as particle accelerators

We examine the possibility of arbitrarily high energy in the center-of-mass (CM) frame of colliding neutral particles in the vicinity of the horizon of a charged dilation black hole (BH). We show that it is possible to achieve the infinite energy in the background of the dilation black hole without fine-tuning of the angular momentum parameter. It is found that the CM energy (Ecm) of collisions of particles near the infinite red-shift surface of the extreme dilation BHs are arbitrarily large while the non-extreme charged dilation BHs have the finite energy. We have also compared the Ecm at the horizon with the ISCO (Innermost Stable Circular Orbit) and MBCO (Marginally Bound Circular Orbit) for extremal Reissner-Nordstrøm (RN) BH and Schwarzschild BH. We find that for extreme RN BH the inequality becomes Ecm|r+>Ecm|rmb>Ecm|rISCO i.e. Ecm|r+=M:Ecmrmb=3+52M:Ecm|rISCO=4M=∞:3.23:2.6. While for Schwarzschild BH the ratio of CM energy is Ecm|r+=2M:Ecm|rmb=4M:Ecm|rISCO=6M=5:2:133. Also for Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) BHs the ratio is being Ecm|r+=2M:Ecm|rmb=2M:Ecm|rISCO=2M=∞:∞:∞.