Experimental analysis of the Strato-rotational Instability in a cylindrical Couette flow

This study is devoted to the experimental analysis of the Strato-rotational Instability (SRI). This instability affects the classical cylindrical Couette flow when the fluid is stably stratified in the axial direction. In agreement with recent theoretical and numerical analyses, we describe for the first time in detail the destabilization of the stratified flow below the Rayleigh line (i.e. the stability threshold without stratification). We confirm that the unstable modes of the SRI are non axisymmetric, oscillatory, and take place as soon as the azimuthal linear velocity decreases along the radial direction. This new instability is relevant for accretion disks.Comment: 4 pages, 4 figures. PRL in press 200

sPlot: a statistical tool to unfold data distributions

The paper advocates the use of a statistical tool dedicated to the exploration of data samples populated by several sources of events. This new technique, called sPlot, is able to unfold the contributions of the different sources to the distribution of a data sample in a given variable. The sPlot tool applies in the context of a Likelihood fit which is performed on the data sample to determine the yields of the various sources.Comment: 27 pages, 8 figures, Accepted for publication in Nucl. Instr. Method