High-energy Particles In Crystal Research Articles

Geometrical optics method in the theory of channeling of high energy particles in crystals

The process of scattering of fast charged particles in thin crystals is considered in the transitional range of thicknesses, between those at which the channeling phenomenon is not developed and those at which it is realized. We demonstrate the possibility of application of the methods of geometrical optics for description of the scattering process. In particular, we study the dependence of the total scattering cross-section of ultrarelativistic positrons on target thickness in this range of crystal thicknesses. In the case of channeling of ultrarelativistic particles we indicate the possibility of the existence of an effect analogical to the Ramsauer-Townsend effect of conversion into zero of the total scattering cross-section at some values of crystal thickness. An important role is noted of the Morse-Maslov index that makes part of the wave function expression in the geometrical optics method.

Spin rotation and depolarization of high-energy particles in crystals at LHC and FCC energies. The possibility to measure the anomalous magnetic moments of short-lived particles and quadrupole moment of [formula omitted]-hyperon

The phenomena of spin rotation and depolarization of high-energy particles in crystals in the range of high energies that will be available at Hadron Collider (LHC) and Future Circular Collider (FCC) provides a unique possibility of measuring the anomalous magnetic moment of charged and neutral charm and beauty hyperons and quadrupole moment of Ω-hyperon. Crystals with polarized nuclei give opportunities for measuring spin-dependent interactions of short lived particles with nuclei and measurement of a particle polarization.

Incoherent bremsstrahlung in flat and bent crystals

Incoherent bremsstrahlung by high-energy particles in crystal is due to the thermal spread of atoms in relation to their equilibrium positions in the lattice. The simulation procedure developed earlier for the incoherent radiation is applied to the case of the electrons and positrons motion in the sinusoidally bent crystal. The results of simulation are in agreement with the data of recent experiments carried out at the Mainz Microtron MAMI. The possibility of use of the sinusoidally bent crystals as undulators is discussed.

Rare processes and coherent phenomena in crystals

We study coherent enhancement of Coulomb excitation of high energy particles in crystals. We develop multiple scattering theory description of coherent excitation which consistently incorporates both the specific resonant properties of particle-crystal interactions and the final/initial state interaction effects typical of the diffractive scattering. Possible applications to observation of induced radiative neutrino transitions are discussed.

Semiclassical approach to the radiation theory of high energy particles in crystals and the boundary conditions problem

A method of canonical transformations for describing the radiation process of high energy particles in an external field and also in crystals using the semiclassical approximation is proposed. The main attention is paid to the problem of the boundary conditions when describing the radiation. It is shown that the radiation cross-section can be expressed through classical particle trajectories in an external field. There may be several trajectories for the same fixed boundary conditions, and the existence of this possibility leads to a specific interference picture of radiation similar to the one for the rainbow scattering of particles.

Stability of motion of high energy particles in crystals and random string approximation

The results of a study of the stability of fast charged particle motion in crystals when the transition occurs from the regular plane motion of a particle in the periodic field of crystal atomic strings to the chaotic motion are presented. The manifestations of such a transition in coherent radiation and the cross sections for pair creation in crystals are discussed. The particle motion pattern in crystals is shown to affect substantially the spectral features of ultrahigh energy electron radiation in crystals.

Production of laser radiation in aligned crystal targets

A number of proposals for the generation of short-wavelength laser radiation by high-energy particles in crystals are examined. Calculation of the gain for each of these proposals indicates that the prospect for observing coherent radiation in such a system is not large.