Steve Biller

Abstract:

The close relation between ground-based TeV observations and satellite borne γ-ray measurements has been important for the understanding of blazars. The observations which involve the TeV component in blazar studies are reviewed. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

Abstract:

A knowledge of the absolute efficiency of the photomultiplier tubes (PMTs) used in the Sudbury Neutrino Observatory (SNO) is important for modelling the behaviour of the detector. While the quantum efficiencies for the PMTs are known, the efficiency in single-photon counting mode (which includes collection efficiency and counting efficiency) is of more relevance. A calibration of the 8 in. Hamamatsu R1408 photomultipliers in this mode requires a known flux of incident light at the very low level of 10-16 W cm-2 (250 photons cm-2 s-1). A method of performing such measurements, utilising the extreme linearity obtainable with silicon photodiodes, is presented in this paper. The results of efficiency measurements on four PMTs are given and a comparison is made with previous results obtained using a Cherenkov source of known intensity.

Abstract:

The ANTARES project is an international collaboration with the aim of building a deep-sea large area neutrino telescope within the next decade. The achievements and status of the project as at the time of the conference are briefly discussed, and short term steps as well as longer term plans are described.

Abstract:

The results of recent studies which seek to probe fundamental aspects of astrophysics using TeV gamma-ray observations of active galactic nuclei (AGN) are presented. These analyses take advantage of both spectral and temporal information together with the unique combination of the very high energies and large distance scales involved. The next generation of instruments currently planned are expected to make substantial improvements in the study of such phenomena. © 1999 Elsevier Science B.V. All rights reserved.

Abstract:

We have used data from a TeV gamma-ray flare associated with the active galaxy Markarian 421 to place bounds on the possible energy dependence of the speed of light in the context of an effective quantum gravitational energy scale. Recent theoretical work suggests that such an energy scale could be less than the Planck mass and perhaps as low as 10^16 GeV. The limits derived here indicate this energy scale to be in excess of 4×106 GeV for at least one approach to quantum gravity in the context of D-brane string theory. To the best of our knowledge this constitutes the first convincing limit on such phenomena in this energy regime. © 1999 The American Physical Society.