Performance of b-tagging algorithms at the CMS experiment with pp collision data at s\sqrt s=8 TeV

The identification of jets originating from b quarks is crucial both for the searches for new physics and for the measurement of standard model processes. The Compact Muon Solenoid (CMS) collaboration at the Large Hadron Collider (LHC) has developed a variety of algorithms to select b-quark jets based on variables such as the impact parameter of charged particle tracks, properties of reconstructed secondary vertices from heavy hadron decays, and the presence or absence of a lepton in the jet, or combinations thereof. Performance measurements of these b-jet identification algorithms are presented, using multijet and $t\overline{t}$ events recorded in proton-proton collision data at $\sqrt s$=8 TeV with the CMS detector during the LHC Run 1

Access of the Poor to Water Supply and Sanitation in India: Salient Concepts, Issues and Cases

Access to safe water is necessary for lives and livelihoods. In India, a mid-term assessment reveals that the country has already met its MDG (Millennium Development Goal) in terms of expanding access to water infrastructure although in the parallel subsector of sanitation progress is falling far short of the mark. In reality, most basic observations indicate that water supply coverage is not as good as the figures show while national sanitation continues to be poor even after almost six decades of efforts to eradicate open defecation. It argues that economic, technical, institutional as well as social factors constrain access to safe drinking water and proper sanitation in India for both the urban and rural poor, and that coverage figures do not reflect this restricted access. It finds that, increasingly, communities are being required to manage their own water and sanitation schemes, not just in rural areas but in urban ones as well. There are definite advantages to such an institutional arrangement if the transition to community management is carried out smoothly. Often, however, the chances of success of community management are vitiated because policy makers misunderstand and misapply three interlinked concepts that are crucial to the success of community-managed water and sanitation schemes?participation; water and sanitation burden; and project ownership. The paper concludes by clarifying these concepts and the implications they have for policy implementation in this sector.Access of the Poor to Water Supply and Sanitation in India: Salient Concepts, Issues and Cases

Algorithms for Secretary Problems on Graphs and Hypergraphs

We examine several online matching problems, with applications to Internet advertising reservation systems. Consider an edge-weighted bipartite graph G, with partite sets L, R. We develop an 8-competitive algorithm for the following secretary problem: Initially given R, and the size of L, the algorithm receives the vertices of L sequentially, in a random order. When a vertex l \in L is seen, all edges incident to l are revealed, together with their weights. The algorithm must immediately either match l to an available vertex of R, or decide that l will remain unmatched. Dimitrov and Plaxton show a 16-competitive algorithm for the transversal matroid secretary problem, which is the special case with weights on vertices, not edges. (Equivalently, one may assume that for each l \in L, the weights on all edges incident to l are identical.) We use a similar algorithm, but simplify and improve the analysis to obtain a better competitive ratio for the more general problem. Perhaps of more interest is the fact that our analysis is easily extended to obtain competitive algorithms for similar problems, such as to find disjoint sets of edges in hypergraphs where edges arrive online. We also introduce secretary problems with adversarially chosen groups. Finally, we give a 2e-competitive algorithm for the secretary problem on graphic matroids, where, with edges appearing online, the goal is to find a maximum-weight acyclic subgraph of a given graph.Comment: 15 pages, 2 figure