Argon and the Periodic System: the Piece that Would not Fit

The discovery of the noble gases and their incorporation into the periodic system are examined in this paper. A chronology of experimental reports on argon and helium and the properties relevant to their nature and position in the periodic system is presented. Proposals on the nature of argon and helium that appeared in the aftermath of their discovery are examined in light of the various empirical and theoretical considerations that supported and contradicted them. ``The piece that would not fit' refers not only to argon, the element that at first seemed not to fit into the periodic system, but also to the piece or pieces of evidence that various researchers and observers were prepared to discard or discount in coming to terms with the newly discovered gases. This revised version was published online in July 2006 with corrections to the Cover Date.     

Superradiance and ferromagnetic behaviour

Summary The ferromagnetic behaviour is analysed in terms of a new physical mechanism based on superradiance. We show that if thed-electrons’ plasma is in a superradiant state, then ferromagnetism arises in transition metals such as Fe, Co and Ni. Satisfactory agreement with experimental information on several important quantities is obtained.     

Reconstruction of cosmic and beam-halo muons with the CMS detector

The powerful muon and tracker systems of the CMS detector together with dedicated reconstruction software allow precise and efficient measurement of muon tracks originating from proton-proton collisions. The standard muon reconstruction algorithms, however, are inadequate to deal with muons that do not originate from collisions. This note discusses the design, implementation, and performance results of a dedicated cosmic muon track reconstruction algorithm, which features pattern recognition optimized for muons that are not coming from the interaction point, i.e., cosmic muons and beam-halo muons. To evaluate the performance of the new algorithm, data taken during Cosmic Challenge phases I and II were studied and compared with simulated cosmic data. In addition, a variety of more general topologies of cosmic muons and beam-halo muons were studied using simulated data to demonstrate some key features of the new algorithm.