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Abstract:

We have performed a search for radiative 6-hadron decays using events produced in ppÌ… collisions at √s=1.8TeV and collected by the Collider Detector at Fermilab. The decays we considered were B^0Ì…d→K^*0(→K^-Ï€⁺γ, B^0Ì…s→φ(→K⁺K^-)γ,⁰b→γ(→p03°ä0^-)γ), and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified by an electron-positron pair produced through the external photon conversion before the tracking detector volume. By combining the two methods we obtain upper limits on the branching fractions for the B^0Ì…d, B^0Ì…s and γ,⁰b radiative decays which, at the 95% confidence level, are found to be B(B^0Ì…d→K^*0γ<1.4×^-4,B(B^0Ì…d→ϵ¥³)<1.6×^-4,and (γ,⁰b→γγ)<1.9×^-3.

Abstract:

We have accumulated multiwavelength lightcurves for eight black hole X-ray binaries which have been observed to enter a supposed ``soft X-ray transient'' outburst, but which in fact remained in the low/hard state throughout the outburst. Comparison of the lightcurve morphologies, spectral behaviour, properties of the QPOs and the radio jet provides the first study of such objects as a subclass of X-ray transients (XRTs). However, rather than assuming that these hard state XRTs are different from ``canonical'' soft XRTs, we prefer to consider the possibility that a new analysis of both soft and hard state XRTs in a spectral context will provide a model capable of explaining the outburst mechanisms for the majority of black hole X-ray binaries.