Kinetic study on self-energy and stopping power of charged particles moving in metallic carbon nanotubes

title: Dynamic interactions of fast ions with carbon nanotubes
abstract: We used the hydrodynamic model to describe the dielectric response of a multi-walled carbon nanotube to a fast point charge moving paraxially, either inside or outside the nanotube. Calculations are performed for a two-walled nanotube, giving rise to a splitting of the plasmon frequencies due to the interaction between the electron fluids on the two cylinders. The dependences of the projectile stopping power and the self-energy (image potential) on the velocity and the distance from the nanotube axis show interesting features when the projectile velocity matches the phase velocity of the plasmon mode with a quasi-linear dispersion.

title: Dynamic interactions of fast ions with multiwalled carbon nanotubes
abstract: We use a two-fluid hydrodynamic model to describe the dielectric response of the σ and π electron systems on a multiwalled carbon nanotube consisting of up to several tens of concentric cylindrical shells. In particular, we evaluate the stopping power and the dynamical image potential for ions moving parallel to the nanotube axis. It is found that both quantities are profoundly affected by the increasing number of nanotube shells, as a consequence of the rich plasmon spectra developed due to the inter- and intra-shell electrostatic interactions between the electron systems.

title: Coulomb explosions and stopping of molecular ions channeled through carbon nanotubes
abstract: We study Coulomb explosions of fast H{sub 2}{sup +} molecules under the channeling conditions through a single-wall carbon nanotube by solving the classical equations of motion for the fragment ions, involving both the repulsive continuum potential of the nanotube wall and the dynamically screened Coulomb repulsion between the two ions. Dynamic polarization of the nanotube electrons, described by a two-dimensional hydrodynamic model, gives rise to the correlated energy losses, a wakelike interaction between the fragment ions, as well as the dynamical image force on each ion. The explosion dynamics is dominated by the bare Coulomb repulsion and it mostly proceeds in the longitudinal direction, accompanied with the radially constrained oscillations of the fragment ions. Strong vicinage effects are found in both the molecule self-energy and its stopping power in the early stages of explosions, but they quickly diminish with the increasing dwell time in a manner which depends on the impact molecule speed and its axis orientation.

title: Interactions of fast ions with carbon nanotubes: Self-energy and stopping power
abstract: The interactions of charged particles with carbon nanotubes are studied by means of the linearized hydrodynamic theory for electronic excitations on the nanotube surface. General expressions are derived for the induced potential, the self-energy, and the stopping power for a charged particle moving paraxially in a nanotube. Numerical results are obtained showing the influence of the damping factor, the nanotube radius, and the particle position on its self-energy and the stopping power. Results for stopping power in the linearized hydrodynamic model are compared with those obtained by means of the dielectric formalism in random-phase approximation, showing a close agreement between the two approaches for high speeds of charged particles.

title: Dynamic polarization effects in ion channeling through single-wall carbon nanotubes
abstract: Ion channeling through a single-wall carbon nanotube is simulated by solving Newton’s equations for ion motion at intermediate energies, under the action of both the surface-atom repulsive forces and the polarization forces due to the dynamic perturbation of the nanotube electrons. The atomic repulsion is described by a continuum potential based on the Thomas-Fermi-Moliere model, whereas the dynamic polarization of the nanotube electrons is described by a two-dimensional hydrodynamic model, giving rise to the transverse dynamic image force and the longitudinal stopping force. In the absence of centrifugal forces, a balance between the image force and the atomic repulsion is found to give rise to ion trajectories which oscillate over peripheral radial regions in the nanotube, provided the ion impact position is not too close to the nanotube wall, the impact angle is sufficiently small, and the incident speed is not too high. Otherwise, the ion is found to oscillate between the nanotube walls, passing over a local maximum of the potential in the center of the nanotube, which results from the image interaction. The full statistical analysis of 10 3 ion trajectories has been made to further demonstrate the actual effect of dynamic polarization on the ion channeling.

title: EXPERIMENTAL STUDY OF HEAVY CHARGED LEPTONS AT PETRA

title: STRONG FIELD EFFECTS ON PULSAR ARRIVAL TIMES: GENERAL ORIENTATIONS
abstract: A pulsar beam passing close to a black hole can provide a probe of very strong gravitational fields even if the pulsar itself is not in a strong field region. In the case that the spin of the hole can be ignored, we have previously shown that all strong field effects on the beam can be understood in terms of two 'universal' functions: F(phi{sub in}) and T(phi{sub in}) of the angle of beam emission phi{sub in}; these functions are universal in that they depend only on a single parameter, the pulsar/black hole distance from which the beam is emitted. Here we apply this formalism to general pulsar-hole-observer geometries, with arbitrary alignment of the pulsar spin axis and arbitrary pulsar beam direction and angular width. We show that the analysis of the observational problem has two distinct elements: (1) the computation of the location and trajectory of an observer-dependent 'keyhole' direction of emission in which a signal can be received by the observer; and (2) the determination of an annulus that represents the set of directions containing beam energy. Examples of each are given along with an example of a specific observational scenario.

title: Observation of $\eta_{c}$ decay into $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$ final states
abstract: Using a data sample of $2.25\times10^{8}$ $J/\psi$ events collected with the BESIII detector, we present the first observation of the decays of $\eta_{c}$ mesons to $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$. The branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $\eta_{c} \to \Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.

title: Measurement of energetic single-photon production at LEP
abstract: We describe the sample of energetic single-photon events (Eγ > 15 GeV) collected by L3 in the 1991–1993 LEP runs. The event distributions agree with expectations from the Standard Model. The data are used to constrain the ZZγ coupling and to set an upper limit of 4.1 × 10−6, μB (90% C.L.) on the the magnetic moment of the τ neutrino.

title: Experimental study of f0(975) in J / psi decays