Coherent and incoherent pair creation by a photon in oriented single crystal

The new approach is developed for study of electron-positron pair production by a photon in oriented single crystal. It permits indivisible consideration of both coherent and incoherent mechanisms of pair creation and includes the action of field of axis (or plane) as well as the multiple scattering of particles of the created pair (the Landau-Pomeranchuk-Migdal (LPM) effect). From obtained integral probability of pair creation, it follows that multiple scattering appears only for relatively low energy of photon, while at higher photon energy the field action excludes the LPM effect. The found results agree quite satisfactory with recent CERN experiment.