QGSJET-II: results for extensive air showers

The new hadronic Monte Carlo model QGSJET-II is applied for extensive air shower (EAS) calculations. The obtained results are compared to the predictions of the original QGSJET and of the SIBYLL 2.1 interaction models. It is shown that non-linear effects change substantially model predictions for hadron-nucleus interactions and produce observable effects for calculated EAS characteristics. Finally the impact of the new model on the interpretation of air shower array data is discussed.Comment: To appear in the proceedings of 13th International Symposium on Very High-Energy Cosmic Ray Interactions at the NESTOR Institute, Pylos, Greece, 6-12 Sep 200

Design And Fabrication Of A Surface-Wave Accelerator Based On Silicon Carbide

The principles and electromagnetic simulations of a novel accelerating structure are described. The structure is planar, consisting of two plates of silicon carbide (SiC) separated by a vacuum gap. Charged particle bunches are accelerated in the vacuum gap by the surface electromagnetic waves (phonon polaritons) localized near the vacuum/SiC interface. The structure can be powered by a carbon dioxide (CO2) laser with the wavelength lambda(0) approximate to 10.6mum. The operating wavelength is dictated by the frequency-dependent dielectric permittivity epsilon(omega) of SiC which is negative for the frequencies in the CO2 tunability range. The resulting accelerator can support accelerating fields well in excess of 1 GeV/m without breakdown, and provide the path to compact and inexpensive particle accelerators. The challenge of coupling radiation into a very narrow (a few microns) vacuum gap is resolved by designing a coupling grating on the top surface of a Si wafer, and attaching a thin SiC film to the bottom of the wafer. Preliminary fabrication results are reported.Physic

A moment problem for discrete nonpositive measures on a finite interval

This article has been made available through the Brunel Open Access Publishing Fund.We will estimate the upper and the lower bounds of the integral ∫01Ω(t)dμ(t), where μ runs over all discrete measures, positive on some cones of generalized convex functions, and satisfying certain moment conditions with respect to a given Chebyshev system. Then we apply these estimations to find the error of optimal shape-preserving interpolation

TOTEM: The experiment to measure the total proton-proton cross section at LHC

The current large uncertainty on the extrapolation of the proton-proton total cross section at the LHC energy will be resolved by the precise measurement by the TOTEM experiment. Its accurate studies on the basic properties of proton-proton collisions at the maximum accelerator energy could provide a significant contribution to the understanding of cosmic ray physics.Comment: 6 pages, 7 figures, Proceedings XIV International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2006), Weihai, China, August 15-22, 200

All-optical suppression of relativistic self-focusing of laser beams in plasmas

It is demonstrated that a catastrophic relativistic self-focusing (RSF) of a high-power laser pulse can be prevented all-optically by a second, much weaker, copropagating pulse. RSF suppression occurs when the difference frequency of the pulses slightly exceeds the electron plasma frequency. The mutual defocusing is caused by the three-dimensional electron density perturbation driven by the laser beat wave slightly above the plasma resonance. A bienvelope model describing the early stage of the mutual defocusing is derived and analyzed. Later stages, characterized by the presence of a strong electromagnetic cascade, are investigated numerically. Stable propagation of the laser pulse with weakly varying spot size and peak amplitude over several Rayleigh lengths is predicted.U.S. Department of Energy DE-FG02-04ER54763 DE-FG02-04ER41321 DE-FG02-07ER54945NSF PHY-0114336Physic

Hadronic Interactions at Cosmic Ray Energies

General physics of very high energy hadronic interactions is discussed. Special attention is payed to the contribution of semihard processes to the interaction dynamics and to the role of parton shadowing and parton density saturation. In particular, the implementation of non-linear interaction effects in the QGSJET-II model is discussed in detail. The predictions of the model are compared to selected accelerator data, including ones of the RHIC collider, and the relation to the calculated extensive air shower characteristics is discussed. Finally, the potential of accelerator and cosmic ray experiments for constraining model predictions is analyzed.Comment: Prepared for the 14th International Symposium on Very High Energy Cosmic Ray Interactions, August 15-22, 2006, Weihai, Chin