Primary Particle Type of the Most Energetic Fly's Eye Air Shower

The longitudinal profile of the most energetic cosmic-ray air shower measured so far, the event recorded by the Fly's Eye detector with a reconstructed primary energy of about 320 EeV, is compared to simulated shower profiles. The calculations are performed with the CORSIKA code and include primary photons and different hadron primaries. For primary photons, preshower formation in the geomagnetic field is additionally treated in detail. For primary hadrons, the hadronic interaction models QGSJET01 and SIBYLL2.1 have been employed. The predicted longitudinal profiles are compared to the observation. A method for testing the hypothesis of a specific primary particle type against the measured profile is described which naturally takes shower fluctuations into account. The Fly's Eye event is compatible with any assumption of a hadron primary between proton and iron nuclei in both interaction models, although differences between QGSJET01 and SIBYLL2.1 in the predicted profiles of lighter nuclei exist. The primary photon profiles differ from the data on a level of ~1.5 sigma. Although not favoured by the observation, the primary photon hypothesis can not be rejected for this particular event.Comment: 20 pages, 8 figures; v2 matches version accepted by Astroparticle Physic

On a possible photon origin of the most-energetic AGASA events

In this work the ultra high energy cosmic ray events recorded by the AGASA experiment are analysed. With detailed simulations of the extensive air showers initiated by photons, the probabilities are determined of the photonic origin of the 6 AGASA events for which the muon densities were measured and the reconstructed energies exceeded 10^20 eV. On this basis a new, preliminary upper limit on the photon fraction in cosmic rays above 10^20 eV is derived and compared to the predictions of exemplary top-down cosmic-ray origin models.Comment: 3 pages, 1 figure, 2 tables; presented at XIII ISVHECRI, Pylos, Greec

Investigation of top mass measurements with the ATLAS detector at LHC

Several methods for the determination of the mass of the top quark with the ATLAS detector at the LHC are presented. All dominant decay channels of the top quark can be explored. The measurements are in most cases dominated by systematic uncertainties. New methods have been developed to control those related to the detector. The results indicate that a total error on the top mass at the level of 1 GeV should be achievable.Comment: 47 pages, 40 figure

Novel concept of multi-channel fiber optic surface plasmon resonance sensor

A novel multi-channel fiber optic surface plasmon resonance (SPR) sensor is reported. The sensing structure consists of a single-mode optical fiber, covered with a thin gold layer, which supports a surface plasmon (SP), and a Bragg grating. The Bragg grating induces coupling between the forward-propagating fundamental core mode and the back-propagating SP-cladding mode. As the SP-cladding modes are highly sensitive to changes in the refractive index of the surrounding medium, the changes can be accurately measured by spectroscopy of these hybrid modes. Multichannel capability is achieved by employing a sequence of Bragg gratings of different periods and their reading via the wavelength division multiplexing. Theoretical analysis and optimization based on the coupled-mode theory (CMT) is carried out and performance characteristics of the sensor are determined