Coherent effects in crystal collimation

We present theory for coherent effects observed in crystal collimation experiments that is in good quantitative agreement with the RHIC and Tevatron data. We show that these effects are caused by a coherent scattering on the field of bent crystal atomic planes, which amplifies beam diffusion in accelerator by orders of magnitude compared to the scattering in amorphous material. This coherent scattering could replace the traditional amorphous scattering in accelerator collimation systems. We predict that for negative particles this effect is as strong as for positive ones, opening a principle way for efficient crystal steering of negative particles at accelerators. Predictions are made for high energy accelerators where crystal collimation is seen as an interesting application.