We calculate the spectrum resulting from the interaction of a fireball with ambient soft photons. These photons are assumed to be produced by the walls of a funnel in a massive star. By parameterizing the radial dependence of the funnel temperature we calculate the deceleration of the fireball self–consistently, taking into account the absorption of high energy γ–rays due to interaction with th...

J. C. Liu, D. Busick1, K. R. Kase, R. C. McCall2, R. Sit and H. Tran3 Stanford Linear Accelerator Center, P. O. Box 4349, Stanford, CA 94309 Abstract The need for providing personnel external monitoring for exposure to lowenergy photon (< 150 keV) and beta radiation at the Stanford Linear Accelerator Center (SLAC) has been studied. At SLAC, a high energy electron accelerator facility, the major...

Many models for ultra-high energy cosmic rays postulate exotic scenarios to explain the sources or the nature of these particles. A characteristic feature of these models is the prediction of a significant flux of photons at ultra-high energy. The Pierre Auger Observatory offers a great potential to search for such photons. We present shower observables with sensitivity to photons and the searc...

Introduction: Image quality and accuracy of in vivo activity quantification in SPECT are affected by collimator penetration and scatter components, especially in high energy imaging. These phenomena highly depend on the collimator characteristic and photon energy. The presence of penetrated and scattered photons from collimator in SPECT images degrades spatial resolution, contr...