WγγW\gamma\gamma Production at the Fermilab Tevatron Collider: Gauge Invariance and Radiation Amplitude Zero

The electroweak process $p\bar p \to \ell^\pm\nu\gamma\gamma$ is calculated at tree level, including finite W width effects. In order to obtain a gauge invariant amplitude, the imaginary parts of $WW\gamma$ triangle graphs and $WW\gamma\gamma$ box diagrams have to be included, in addition to resumming the imaginary contributions to the W polarization. We demonstrate the existence of a radiation amplitude zero in $p\bar p \to W^\pm \gamma\gamma \to \ell^\pm\nu\gamma\gamma$, and discuss how it may be observed in correlations of the $\gamma\gamma$ and lepton rapidities at the Fermilab Tevatron.Comment: 37 pages,12 figures, postscript file also available via anonymous ftp at ftp://ucdhep.ucdavis.edu/han/vvv/Wgmgm.p

Sistemas operacionais

Ao longo de mais de 40 anos, sistemas operacionais têm sido desenvolvidos com o propósito de tornar a utilização do computador mais eficiente e mais conveniente. Para isso, um enorme número de conceitos, abstrações, mecanismos e algoritmos foram criados e aprimorados. Este artigo é um tutorial a respeito das técnicas fundamentais empregadas nos sistemas operacionais contemporâneos. Também são discutidos aqui os sistemas operacionais distribuídos e de tempo real.For more than 40 years, operating systems have been developed with the goal of making the utilization of computers more efficient and more comfortable. A huge number of concepts, abstractions, mechanisms and algorithms were created and improved. This paper is a tutorial on the fundamental techniques applied in the construction of contemporary operating systems. We also discuss distributed operating systems and real-time operating system